verify gunicorn is in requirements.txt before adding as a start command

[gilzow]

G/ is reporting that when upsun project:init detected his code as a Flask stack, the written config file included:

start: "gunicorn -b unix:$SOCKET 'app:app' --log-file -"

for web:commands:start. HOWEVER, upsun project:init did not verify that gunicorn was included in the requirements.txt and therefore the app failed to start correctly.

We need to verify that gunicorn is in requirements before adding gunicorn start command, or at least warn the user to make sure it is included.

[gmoigneu]

Another option would be to include the gunicorn in the python3 dependencies in the yaml.

[gilzow]

what happens if we end up with it in both places? 🤔

[akalipetis]

I am against including dependencies for the user - we should handle the case where Gunicorn is missing, but not install it for them.

[gilzow]

re-opened as the issue is still valid (linear should not have closed the issue)