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Django manage.py migrate errors

I've been working on a project for CS50-Web for a while now and I was changing some of my models trying to add a unique attribute to some things. Long story short it wasn't working how I wanted so I went back to how I had it previously and now something is wrong and I can get it to migrate the changes to the model. I don't understand what to do because it was working fine before. Please can someone help I so frustrated and annoyed that I've broken it after so many hours of work. Sorry I know this error code is long but I don't know which part is important.
Error code
Operations to perform:
Apply all migrations: admin, auth, contenttypes, network, sessions
Running migrations:
Applying network.0019_alter_follower_user...Traceback (most recent call last):
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\sqlite3\base.py", line 416, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.IntegrityError: UNIQUE constraint failed: new__network_follower.user_id
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "C:\Users\caitw\Documents\GitHub\CS50-Web\Project-4-Network\project4\manage.py", line 21, in <module>
main()
File "C:\Users\caitw\Documents\GitHub\CS50-Web\Project-4-Network\project4\manage.py", line 17, in main
execute_from_command_line(sys.argv)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\core\management\__init__.py", line 425, in execute_from_command_line
utility.execute()
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\core\management\__init__.py", line 419, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\core\management\base.py", line 373, in run_from_argv
self.execute(*args, **cmd_options)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\core\management\base.py", line 417, in execute
output = self.handle(*args, **options)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\core\management\base.py", line 90, in wrapped
res = handle_func(*args, **kwargs)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\core\management\commands\migrate.py", line 253, in handle
post_migrate_state = executor.migrate(
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\migrations\executor.py", line 126, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\migrations\executor.py", line 156, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\migrations\executor.py", line 236, in apply_migration
state = migration.apply(state, schema_editor)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\migrations\migration.py", line 125, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\migrations\operations\fields.py", line 225, in database_forwards
schema_editor.alter_field(from_model, from_field, to_field)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\sqlite3\schema.py", line 140, in alter_field
super().alter_field(model, old_field, new_field, strict=strict)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\base\schema.py", line 620, in alter_field
self._alter_field(model, old_field, new_field, old_type, new_type,
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\sqlite3\schema.py", line 362, in _alter_field
self._remake_table(model, alter_field=(old_field, new_field))
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\sqlite3\schema.py", line 285, in _remake_table
self.execute("INSERT INTO %s (%s) SELECT %s FROM %s" % (
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\base\schema.py", line 153, in execute
cursor.execute(sql, params)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\utils.py", line 99, in execute
return super().execute(sql, params)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\utils.py", line 67, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\utils.py", line 76, in _execute_with_wrappers
return executor(sql, params, many, context)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\utils.py", line 90, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "C:\Users\caitw\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\django\db\backends\sqlite3\base.py", line 416, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: UNIQUE constraint failed: new__network_follower.user_id
I went back to how I had the code before it failed but it doesn't work now

Just try these 3 commands for migrations:
python manage.py makemigrations appname
python manage.py sqlmigrate appname 0001 #This value will generate afte makemigrations. it can be either 0001, 0002 or more.
python manage.py migrate
And see if it solves this error

django.db.utils.ProgrammingError: relation "app_bugs" already exists

After I deleted all the migration files and made them again using "python3 manage.py makemigrations" and "python3 manage.py migrate", the following error occurred:
root#chat-manager:/var/www/jinabot# python3 manage.py migrate
Operations to perform:
Apply all migrations: admin, app, auth, contenttypes, sessions
Running migrations:
Applying app.0002_auto_20220604_2133...Traceback (most recent call last):
File "/usr/local/lib/python3.7/dist-packages/django/db/backends/utils.py", line 82, in _execute
return self.cursor.execute(sql)
psycopg2.errors.DuplicateTable: relation "app_bugs" already exists
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 23, in <module>
main()
File "manage.py", line 19, in main
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.7/dist-packages/django/core/management/__init__.py", line 419, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.7/dist-packages/django/core/management/__init__.py", line 413, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python3.7/dist-packages/django/core/management/base.py", line 354, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/lib/python3.7/dist-packages/django/core/management/base.py", line 398, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python3.7/dist-packages/django/core/management/base.py", line 89, in wrapped
res = handle_func(*args, **kwargs)
File "/usr/local/lib/python3.7/dist-packages/django/core/management/commands/migrate.py", line 246, in handle
fake_initial=fake_initial,
File "/usr/local/lib/python3.7/dist-packages/django/db/migrations/executor.py", line 117, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
File "/usr/local/lib/python3.7/dist-packages/django/db/migrations/executor.py", line 147, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "/usr/local/lib/python3.7/dist-packages/django/db/migrations/executor.py", line 227, in apply_migration
state = migration.apply(state, schema_editor)
File "/usr/local/lib/python3.7/dist-packages/django/db/migrations/migration.py", line 126, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "/usr/local/lib/python3.7/dist-packages/django/db/migrations/operations/models.py", line 92, in database_forwards
schema_editor.create_model(model)
File "/usr/local/lib/python3.7/dist-packages/django/db/backends/base/schema.py", line 331, in create_model
self.execute(sql, params or None)
File "/usr/local/lib/python3.7/dist-packages/django/db/backends/base/schema.py", line 145, in execute
cursor.execute(sql, params)
File "/usr/local/lib/python3.7/dist-packages/django/db/backends/utils.py", line 66, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "/usr/local/lib/python3.7/dist-packages/django/db/backends/utils.py", line 75, in _execute_with_wrappers
return executor(sql, params, many, context)
File "/usr/local/lib/python3.7/dist-packages/django/db/backends/utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.7/dist-packages/django/db/utils.py", line 90, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/usr/local/lib/python3.7/dist-packages/django/db/backends/utils.py", line 82, in _execute
return self.cursor.execute(sql)
django.db.utils.ProgrammingError: relation "app_bugs" already exists
How to fix it?
..................................................................

In database, the relation has already been created. You might have two references for bugs relation in your django app models.py file. If you find multiple reference please rename it differently.
If it's isn't the case you can resolve the error in 2 days:
Delete database entirely. If you're using sqlite3 db then just delete db.sqlite3 file present in your project directory.
Delete all migrations file entirely and recreate and apply it.

Can't migrate after makemigrations on django

everyone. I newbie in this field. So, After I finished makemigrations. then I migrate this error code occurs. I try to solve it but still stuck. please guide, I attach my error code as below.
(venv) C:\Users\hp\Desktop\Taskly_App\src>python manage.py migrate
Operations to perform:
Apply all migrations: admin, auth, contenttypes, house, oauth2_provider, sessions, social_django, task, users
Running migrations:
Applying task.0002_auto_20210331_2329...Traceback (most recent call last):
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\backends\utils.py", line 82, in _execute
return self.cursor.execute(sql)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\backends\sqlite3\base.py", line 411, in execute
return Database.Cursor.execute(self, query)
sqlite3.OperationalError: table "task_tasklist" already exists
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 22, in <module>
main()
File "manage.py", line 18, in main
execute_from_command_line(sys.argv)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\core\management\__init__.py", line 401, in execute_from_command_line
utility.execute()
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\core\management\__init__.py", line 395, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\core\management\base.py", line 330, in run_from_argv
self.execute(*args, **cmd_options)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\core\management\base.py", line 371, in execute
output = self.handle(*args, **options)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\core\management\base.py", line 85, in wrapped
res = handle_func(*args, **kwargs)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\core\management\commands\migrate.py", line 243, in handle
post_migrate_state = executor.migrate(
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\migrations\executor.py", line 117, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\migrations\executor.py", line 147, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\migrations\executor.py", line 227, in apply_migration
state = migration.apply(state, schema_editor)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\migrations\migration.py", line 124, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\migrations\operations\models.py", line 92, in database_forwards
schema_editor.create_model(model)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\backends\base\schema.py", line 324, in create_model
self.execute(sql, params or None)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\backends\base\schema.py", line 142, in execute
cursor.execute(sql, params)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\backends\utils.py", line 98, in execute
return executor(sql, params, many, context)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\backends\utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\utils.py", line 90, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\backends\utils.py", line 82, in _execute
return self.cursor.execute(sql)
File "C:\Users\hp\Desktop\Taskly_App\venv\lib\site-packages\django\db\backends\sqlite3\base.py", line 411, in execute
return Database.Cursor.execute(self, query)
django.db.utils.OperationalError: table "task_tasklist" already exists
I don't know task_tasklist error is mean.
Please help me!!

The error message speak for itself:
The table "task_tasklist" already exists in our DB

OperationalError during django migration postgres on large tables

Sometimes during migrations in django on big tables (>50 millions rows) i receive the following error:
Traceback:
Traceback (most recent call last):
File "src/audit/manage.py", line 22, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 363, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 355, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 283, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 330, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/commands/migrate.py", line 204, in handle
fake_initial=fake_initial,
File "/usr/local/lib/python3.5/dist-packages/django/db/migrations/executor.py", line 115, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
File "/usr/local/lib/python3.5/dist-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "/usr/local/lib/python3.5/dist-packages/django/db/migrations/executor.py", line 244, in apply_migration
state = migration.apply(state, schema_editor)
File "/usr/local/lib/python3.5/dist-packages/django/db/migrations/migration.py", line 129, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "/usr/local/lib/python3.5/dist-packages/django/db/migrations/operations/fields.py", line 86, in database_forwards
field,
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/base/schema.py", line 439, in add_field
self.execute(sql)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/base/schema.py", line 120, in execute
cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 80, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/usr/local/lib/python3.5/dist-packages/django/utils/six.py", line 685, in reraise
raise value.with_traceback(tb)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
django.db.utils.OperationalError: server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
Can you please give me advice - which postgres settings i should change in order to solve this issue?
I try set statement_timeout = 0, idle_in_transaction_session_timeout = 0 with no result.
Migration:
class Migration(migrations.Migration):
dependencies = [
('core', '0028_auto_'),
]
operations = [
migrations.AddField(
model_name='risk',
name='test3',
field=models.CharField(default='testme', max_length=50),
),
]
SQL:
BEGIN;
--
-- Add field test3 to risk
--
ALTER TABLE "core_risk" ADD COLUMN "test3" varchar(50) DEFAULT 'testme' NOT NULL;
ALTER TABLE "core_risk" ALTER COLUMN "test3" DROP DEFAULT;
COMMIT;

django changing a date field to integer field can't migrate

I recently changed a date field to an integer field (the data was specified in number of months remaining rather than a date).
However all though the make migrations command works fine when I attempt to migrate this fails with a typecast error (note using postgres 9.5). Note there was only 1 instance/entry of the model, which I have also now deleted and the migrate still fails for some reason?
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
psycopg2.ProgrammingError: cannot cast type date to integer
LINE 1: ...end_date_fixed" TYPE integer USING "end_date_fixed"::integer
^
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
utility.execute()
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/core/management/__init__.py", line 345, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/core/management/base.py", line 348, in run_from_argv
self.execute(*args, **cmd_options)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/core/management/base.py", line 399, in execute
output = self.handle(*args, **options)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/core/management/commands/migrate.py", line 200, in handle
executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/migrations/executor.py", line 92, in migrate
self._migrate_all_forwards(plan, full_plan, fake=fake, fake_initial=fake_initial)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/migrations/executor.py", line 121, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/migrations/executor.py", line 198, in apply_migration
state = migration.apply(state, schema_editor)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/migrations/migration.py", line 123, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/migrations/operations/fields.py", line 201, in database_forwards
schema_editor.alter_field(from_model, from_field, to_field)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/backends/base/schema.py", line 482, in alter_field
old_db_params, new_db_params, strict)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/backends/postgresql/schema.py", line 110, in _alter_field
new_db_params, strict,
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/backends/base/schema.py", line 634, in _alter_field
params,
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/backends/base/schema.py", line 110, in execute
cursor.execute(sql, params)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/backends/utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/utils.py", line 95, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/utils/six.py", line 685, in reraise
raise value.with_traceback(tb)
File "/Users/Yunti/.virtualenvs/switcher5/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: cannot cast type date to integer
LINE 1: ...end_date_fixed" TYPE integer USING "end_date_fixed"::integer

If the table is empty.
Do the migration in two simple steps. Step 1, drop the existing date column from the model. Step 2 add a new INTEGER column with the same column name.
If the table is not empty.
Edit your model to change the type of end_date_fixed to integer as you have done. Do the make migrations, the open the migrations and delete everything inside migrations[] then replacce it with
migrations.RunSQL("ALTER TABLE mytable ALTER end_date_fixed TYPE INTEGER USING EXTRACT(epoch FROM end_date_fixed)
Make sure that you have not made any other changes to the model when you try this method.