fixed typo on docstring
Fixes #21833 -- Fix UserSettingsHolder.is_overridden() and add tests.
Fix a check_framework test so it doesn't fail when TEST_RUNNER is set (e.g. on CI).
Removed some stray newlines which caused flake8 issues
Changed django-admin back to django-admin.py. Refs #21827
Corrected problem with MySQL checks handler and related fields.
Merge pull request #2186 from zemanel/master

Fixed typo on docstring
Fixed #21827 -- Install django-admin and django-admin.py

We need to figure out how to deprecate django-admin.py, but for now this
should do the trick.
Fixed #21852 -- Make migration writer serialize iterators
Fixed #21850 -- Made GeometryField.geodetic case insensitive
Merge pull request #2198 from Markush2010/ticket21852

Fixed #21852 -- Make migration writer serialize iterators
Fixed #21846 -- Made NestedObjects handle related_name with %(app_label)s or %(class)s.
Fixed some markup that caused broken links in the static files docs.
Fixed #21726 -- Clarified that password should not be included in REQUIRED_FIELDS.

Thanks russellm for the report.
Added some missing whitespace around arithmetic operators
Fixed #21529 -- Noted that {% url %} encodes its output (refs #13260).
Added a link to the 1.6 release notes which also fixed a rendering issue.
Fixed #20834 -- Described how caching of user permissions works.

Thanks Giggaflop and Jennifer Casavantes.
Don't show `self` in the list of arguments of a method.

This is consistent with Python's official documentation
and it's a sphinx recommendation too[1].

[1] http://sphinx-doc.org/markup/desc.html#dir-method

Refs #21855.
Always use parentheses when documenting a method with no arguments.