* 🔧 Add pre-commit config
Similar to graphene and graphene-sqlalchemy
* ⬆ Bump black
* 👷 Lint on CI
* ⬆ Bump flake8-black
* 🔧 Keep excluding migrations
* ⬆ Bump flake8
* 🔧 Remove black and flake8 from tox config
* ⬆ Update pre-commit versions
* Upgrade syntax to python 3.7+
* Format with pre-commit
dedent docs/schema.py to allow formatting
* Fix tests on python 3.7
* Remove Python 2 support
* Upgrade Python & Django versions
* Remove unsupported Django versions
* Remove unsupported Python versions
* Add Python 3.8
* Drop support for django-filter < 2
* Update LoginRequiredMixin doc link
* Remove redundant import
* Resolve RemovedInDjango40Warning warnings
* gql/graphene-django/graphene_django/tests/test_converter.py:175:
RemovedInDjango40Warning: django.utils.translation.ugettext_lazy() is
deprecated in favor of django.utils.translation.gettext_lazy().
* graphene-django/graphene_django/utils/utils.py:28:
RemovedInDjango40Warning: force_text() is deprecated in favor of
force_str().
* No need to use unicode strings with Python3
* Remove singledispatch dependency
singledispatch is inluded with Python >= 3.4, no need for external
package.