Drop Python 2 support + update primary deployment to Python 3

[kracekumar]

Previously Junction worked on Python 2 and Python 3 but deployed only in python 2 in server. From now use only Python 3 in server and remove support for Python 2 and update requirements.

• Drop Python 2 support and enable Python 3 support.
• Migrate server to Python 3(magudi).
• Upgrade packages and refactor the code.
• Deploy to the server.
• Update any relevant documentation

[ananyo2012]

I think #622 addresses the CI tests for this. The original PR #615 made by Krace checks for py 3.6 and 3.7 as well. @pradyunsg What do you think regarding supporting those versions ?

[pradyunsg]

I'm on board for being Python 3.5+ compatible.

I do think it'd be a good idea to stick to a single Python version though, and 3.8 is a good target as of today.

[ananyo2012]

@palnabarun Please close this issue once the prod migration to Python 3 is done

[inovizz]

What is the current state of this issue? Is there anything I can help here?

[pradyunsg]

No movement since Jun, I think.

#686
#687
#667

These seem relevant, though I imagine there's more stuff. :)

[ananyo2012]

Junction upgrade to Django 3.2 and python 3.10 is complete. Thanks to all who contributed in this huge task.