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webpack and django on Heroku: bundling before collectstatic

I am building a django+react app on Heroku, using django-npm which automatically installs all modules from package.json to node-modules dir and then copies everything to staticfiles/ during python manage.py collectstatic (which is triggered by Heroku during deploy).
However, for this configuration to work I need to pre-bundle my React app before deployment and put it into my static folder along with all the CSS, fonts, etc. to be picked up by collectstatic later.
But I don't want to pollute my git diffs with new bundle versions. So, is there a way to make webpack create a bundle during deployment?
I know there is a release command on Heroku where I can put my npm run build. But the problem is it only fires AFTER collectstatic, so my bundle will only be created in static/ folder after this folder is scanned, and won't get copied to staticfiles dir.

Update:
Using bin/pre_compile should no longer be necessary as of March 11, 2019. Heroku will now automatically call an app's build script (if defined in package.json) during Heroku's build process. Source: Heroku Changelog.
Original: You can accomplish this with the (undocumented) pre_compile hook exposed by the heroku/python buildpack.
Add an executable shell file named bin/pre_compile at the top level of your app and it will be called automatically as part of the build process.
cd my-django-app
mkdir bin
echo '#!/usr/bin/env bash' >> bin/pre_compile
echo 'npm run build' >> bin/pre_compile
chmod +x bin/pre_compile

Running Django locally with heroku fails due to missing Procfile

I have a Django 1.11/Python 3.5 app that I built and want to run on Heroku locally. It's a simple SPA using the Heroku Django template provided on GitHub (https://github.com/heroku/heroku-django-template). I followed a Heroku tutorial (https://devcenter.heroku.com/articles/deploying-python#how-to-keep-build-artifacts-out-of-git), but I cannot seem to run the app locally using the following command:
heroku local web
Running this produces the following error:
return binding.open(pathModule._makeLong(path), stringToFlags(flags), mode);
^
Error: EACCES: permission denied, open '.env'
at Object.fs.openSync (fs.js:584:18)
at Object.fs.readFileSync (fs.js:491:33)
at loadEnvsFile (/snap/heroku/414/lib/node_modules/heroku-cli/node_modules/foreman/lib/envs.js:133:15)
at Array.map (native)
at loadEnvs (/snap/heroku/414/lib/node_modules/heroku-cli/node_modules/foreman/lib/envs.js:148:30)
at Command.<anonymous> (/snap/heroku/414/lib/node_modules/heroku-cli/node_modules/foreman/nf.js:72:16)
at Command.listener (/snap/heroku/414/lib/node_modules/heroku-cli/node_modules/commander/index.js:301:8)
at emitTwo (events.js:106:13)
at Command.emit (events.js:194:7)
at Command.parseArgs (/snap/heroku/414/lib/node_modules/heroku-cli/node_modules/commander/index.js:615:12)
My .env file looks like this:
WEB_CONCURRENCY=3
SECRET_APP_KEY="xxxxxxxxxxxxxxxxxxxx"
I ran chmod 777 on .env but I get the same error.
When I run the following command:
heroku local
I get the following error:
[WARN] EACCES: permission denied, open 'Procfile'
[FAIL] No Procfile and no package.json file found in Current Directory - See run.js --help
▸ Cannot convert undefined or null to object
My Procfile looks like this:
web: gunicorn personal_website.wsgi
Now I cannot understand why when running "heroku local web" I get the previously mentioned error, especially after giving it the necessary permissions.
Also, others have had the same error when running "heroku local", but the answer is to "make sure the formatting of your Procfile is correct." Well mine is correct and have tried many variations to it.
I have seen others with this issue on SO and some have been resolved, unfortunately for me none of them worked.
What could I possibly be doing wrong here?

Deploying a simple python script to Heroku without Flask or Django

I'm trying to deploy a python script, but I get this error
Failed to detect app matching https://codon-buildpacks.s3.amazonaws.com/buildpacks/heroku/python.tgz buildpack
What files I have right now:
automation.py
A simple python script which imports praw, time, os and inspect.
requirements.txt
As described in the Heroku documents, I have created this file by running pip freeze > requirements.txt, containing:
astroid==1.5.2
colorama==0.3.8
isort==4.2.5
lazy-object-proxy==1.2.2
mccabe==0.6.1
praw==4.4.1.dev0
prawcore==0.10.1
pylint==1.7.1
requests==2.13.0
six==1.10.0
update-checker==0.16
wrapt==1.10.10
runtime.txt
Again as described in Heroku documents, this file contains the runtime for my script, containing:
python-3.6.0
I have changed my remote to heroku, added all files, commited and pushed to heroku master, but I get the error mentioned in the beginning. Is there something I'm doing wrong? I have seen this answer, but I'm not convinced. Would like to avoid any frameworks if possible.
git ls-files output
.gitignore
LICENSE
README.md
requirements.txt
runtime.txt
automation.py

In addition to runtime.txt and requirements.txt, a Procfile is required - that's how Heroku knows what script to run for your app. Without it, Heroku doesn't know automation.py is anything special. Note though - if your script doesn't listen on any port, define the process name as "worker" or anything other than "web". If you define it as "web" Heroku will expect it to bind to an externally visible port (not on localhost). If Heroku doesn't detect a port bind within 60 seconds, it reports the app as failed to start

Git command when translating files in Django

I have an existing application in Django.
I want to add a translation on the page.
On page I have:
{% trans 'Projects'%}
In .po file I added:
#: templates/staff/site.html: 200
msgid "Projects"
msgid "Projekty"
Then executes the command:
django-admin.py compilemessages -l pl
After this command, I get an error:
CommandError: This Should Be Run script from the Django Git checkout or your project or app tree, or with the settings Specified module.

$ python manage.py compilemessages --settings nsp.settings
CommandError: This script should be run from the Django Git checkout or your project or app tree, or with the settings module specified.
I have got this error while I truly was inside project root folder.
The problem was, that I was running this command without python manage.py makemessages first.
The error message is misleading.

The error holds the answer, you could be running the script from anywhere so it cannot know which files to compile. Run the command from the project directory or specify the settings and you should be fine.

If you are using docker containers to build and deploy your application you should copy folder:
conf/
from root folder of your django project.
with the conf folder you should see i.e:
processing file django.po in /gamma/conf/locale/en/LC_MESSAGES
processing file django.po in /gamma/conf/locale/es/LC_MESSAGES
processing file django.po in /gamma/conf/locale/pt_BR/
without the conf folder you should see a clueless message like that:
CommandError: This script should be run from the Django Git checkout or your project or app tree, or with the settings module specified.

The error message is saying that it could not find the translations files where it expected them to be. Check that everything is correctly setup:
LOCALE_PATHS is defined in your settings.py
the files exist in the folder defined above (created by running python manage.py makemessages)
actually the error goes away even with just an empty locales folder
the compilemessages command is run from the project root folder

If you haven't set LOCALE_PATHS in your settings file, you need to do so:
import os
LOCALE_PATHS = [os.path.join(BASE_DIR, 'locale')]

Django Heroku push failing

I'm running accross an error trying to push my Django project up to Heroku and I was looking to see if anyone had any insight.
! Heroku push rejected, no Cedar-supported app detected
I am guessing it is because of my folder structure in the git repo but I am not sure. My project is setup like this:
/subfolder/djangoproject/
/subfolder/requirements.txt
My Proc file content looks like this:
web: python manage.py runserver 0.0.0.0:$PORT --noreload --settings=djangoproject.settings.heroku
I have my project setting split and they work fine on my local. (In other words I having a setting directory with an init.py in it.)
I tried this:
/Procfile
and this:
/subfolder/Procfile
but neither worked.
Can this folder structure be the culprit? I was under the impression that the requirements.txt was how Heroku found where the project folder was.
Thanks
I wanted to add my solve for the first issue I had and then post the new issue I am having.
The solve I first did was to move the Procfile and requirements.txt files to the root level of the project. The second thing I did was edit the Procfile in so the path to the manage.py script was to the proper location
web: python subfolder/djangoproject/manage.py runserver 0.0.0.0:$PORT --noreload --settings=djangoproject.settings.heroku
I've hit a new error now when trying to run a syncdb. It seems to go through the process but nothing takes. In other words, if I run syncdb once and then run it a second time, it wants to set everything up all over again. Any thoughts on what I may have configures wrong to make the DB not save it's data? Should I use the setting for the DB from the dashboard or keep this line in the Django config:
import dj_database_url
DATABASES['default'] = dj_database_url.config()
Thanks

You need requirements.txt or setup.py in the root of the repo.
See https://github.com/heroku/heroku-buildpack-python/blob/master/bin/detect