django-polymorphic now does support Django>3.0

[n2ygk]

I don't use polymorphic but noticed that the docs build was failing with this traceback:

Traceback (most recent call last):
  File "/Users/alan/src/kezy182/.tox/docs/lib/python3.6/site-packages/sphinx/config.py", line 319, in eval_config_file
    execfile_(filename, namespace)
  File "/Users/alan/src/kezy182/.tox/docs/lib/python3.6/site-packages/sphinx/util/pycompat.py", line 88, in execfile_
    exec(code, _globals)
  File "/Users/alan/src/kezy182/docs/conf.py", line 31, in <module>
    django.setup()
  File "/Users/alan/src/kezy182/.tox/docs/lib/python3.6/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/Users/alan/src/kezy182/.tox/docs/lib/python3.6/site-packages/django/apps/registry.py", line 114, in populate
    app_config.import_models()
  File "/Users/alan/src/kezy182/.tox/docs/lib/python3.6/site-packages/django/apps/config.py", line 211, in import_models
    self.models_module = import_module(models_module_name)
  File "/Users/ac45/.pyenv/versions/3.6.10/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/Users/alan/src/kezy182/.tox/docs/lib/python3.6/site-packages/polymorphic/models.py", line 17, in <module>
    from .base import PolymorphicModelBase
  File "/Users/alan/src/kezy182/.tox/docs/lib/python3.6/site-packages/polymorphic/base.py", line 18, in <module>
    from .managers import PolymorphicManager
  File "/Users/alan/src/kezy182/.tox/docs/lib/python3.6/site-packages/polymorphic/managers.py", line 10, in <module>
    from polymorphic.query import PolymorphicQuerySet
  File "/Users/alan/src/kezy182/.tox/docs/lib/python3.6/site-packages/polymorphic/query.py", line 11, in <module>
    from django.db.models import FieldDoesNotExist
ImportError: cannot import name 'FieldDoesNotExist'

I worked around this by forcing Django>=2.2,<3.0 to get the docs built. PR coming shortly.

[n2ygk]

Django Polymorphhic 3.0 now supports Django 3.0 but drops 1.11.

Looks like it's time to drop 1.11....

[sliverc]

Dropping support for Django 1.11 is certainly good as it is end of life.

However dropping of Django 1.11 support would mean another major release as it drops backwards compatibility. That's totally fine but I would like to combine it with adding support for DRF 3.12 as well. Hope this is coming out soon but I guess we won't release before it is not released.

[n2ygk]

@sliverc yep. I took the opportunity to create a 3.3.0 milestone.

[sliverc]

we are following semver (unlike DRF) so it should be version 4.0.0.

[sliverc]

As of changes made in #828 and #831 this issue is also resolved.