feat: remove support for python 2.7, add support for Python 3.9 & Django 3.1, 3.2

[galuszkak]

Hi @chrisjones-brack3t @kennethlove ,

This is mostly maintenance PR. I've tried to make sure everything is passing tests. Would be really grateful for review.

Thanks

[ghost]

Thanks!
It helped me to get rid of such an exception

File "C:\Users\user\AppData\Local\Programs\Python\Python38-32\lib\site-packages\advanced_filters\views.py", line 11, in <module>
    from braces.views import (CsrfExemptMixin, StaffuserRequiredMixin,
  File "C:\Users\user\AppData\Local\Programs\Python\Python38-32\lib\site-packages\braces\views\__init__.py", line 3, in <module>
    from ._access import (
  File "C:\Users\user\AppData\Local\Programs\Python\Python38-32\lib\site-packages\braces\views\_access.py", line 13, in <module>
    from django.utils import six
ImportError: cannot import name 'six' from 'django.utils' 

Note to other users!

[galuszkak]

Hi @kennethlove @chrisjones-brack3t ,

Kind reminder.

[galuszkak]

Hi @kennethlove @chrisjones-brack3t ,

I've updated again this PR now with Python 3.9 and Django 3.2 and asking very kindly for review & merge.

Please also enable back new TravisCI (they migrated from Travis-CI.org to travis-ci.com and you have to re-enable it in new domain.).

If you need any help let me know.

[galuszkak]

Hi @kennethlove @chrisjones-brack3t ,

Kind reminder, thanks for all hard work on this project.

[kennethlove]

Sorry @galuszkak, we've both been tied up with family and work and this project is stable, so we don't check it often. I'll do my best to get your PR and others read and approved this week.

[galuszkak]

Hi @kennethlove, thanks for taking time on this. I know how much time open-source takes from private life so even more gratitude from me for looking into this.

[chrisjones-brack3t]

Starting to look at this today. 👍🏻