Add test for missing typing import when used m2m to contrib auth

[b0g3r]

In my project, we use a combination of:

• Models with custom managers
• Custom managers built on custom querysets and .from_queryset
• Custom querysets inherited from base queryset

And if we add to this combination custom User Model with a FK (or m2m) link to any model from django.contrib.auth then we get "name is not defined" errors like Name 'Union' is not defined

Raw test output

============================= test session starts ==============================
platform darwin -- Python 3.7.5, pytest-5.3.2, py-1.8.0, pluggy-0.13.1 -- /Users/Boger/venvs/django-stubs/bin/python
cachedir: .pytest_cache
rootdir: /Users/Boger/PycharmProjects/django-stubs, inifile: pytest.ini
plugins: mypy-plugins-1.2.0
collecting ... collected 149 items / 148 deselected / 1 selected

test-data/typecheck/managers/querysets/test_from_queryset.yml::from_queryset_with_inherited_manager_and_fk_to_auth_contrib FAILED
test-data/typecheck/managers/querysets/test_from_queryset.yml:None (from_queryset_with_inherited_manager_and_fk_to_auth_contrib)
/Users/Boger/PycharmProjects/django-stubs/test-data/typecheck/managers/querysets/test_from_queryset.yml:188: 
E   pytest_mypy.utils.TypecheckAssertionError: Invalid output: 
E   Expected:
E     main:2: note: Revealed type is 'myapp.models.MyModel_NewManager[myapp.models.MyModel]'
E     main:3: note: Revealed type is 'myapp.models.MyModel*'
E     main:4: note: Revealed type is 'def (param: Union[builtins.int, builtins.str]) -> Union[builtins.int, builtins.str]' (diff)
E     main:5: note: Revealed type is 'Union[builtins.int, builtins.str]' (diff)
E   Actual:
E     main:2: note: Revealed type is 'myapp.models.MyModel_NewManager[myapp.models.MyModel]'
E     main:3: note: Revealed type is 'myapp.models.MyModel*'
E     main:4: note: Revealed type is 'def (param: Any) -> Any' (diff)
E     main:5: note: Revealed type is 'Any'          (diff)
E     myapp/managers:4: error: Name 'Union' is not defined (diff)
E     myapp/managers:4: note: Did you forget to import it from "typing"? (Suggestion: "from typing import Union") (diff)
E   
E   Alignment of first line difference:
E     E: ...ed type is 'def (param: Union[builtins.int, builtins.str]) -> Union[b...
E     A: ...ed type is 'def (param: Any) -> Any'...
E                                   ^

Steps to reproduce:

• Create Queryset with typing and typing import
• Use .from_queryset in another file
• Create a model with FK to django.auth.contrib anywhere