That test might not always execute, but can be executed when the
parent test label is explicitely given.

Thanks dfunckt and Tim Graham.

Previously a RuntimeError was raised every time two models clashed
in the app registry. This prevented reloading a module in a REPL;
while it's not recommended to do so, we decided not to forbid this
use-case by turning the error into a warning.

Thanks @dfunckt and Sergey Pashinin for the initial patches.

Thanks prathik for the report.

This includes the following improvements:

- The type of the style object is now called 'Style' rather than 'dummy'.
- The new make_style() function allows generating a Style object directly
  from a config string. Before the only way to get a style object was
  through the environ and it also required that the terminal supported
  colors which isn't necessarily the case when testing.
- The output of no_style() is now cached with @lru_cache.
- The output of no_style() now has the same set of attributes as the
  other Style objects. Previously it allowed anything to pass through
  with __getattr__.

Thanks Tim Graham for the review.

This is a leftover from 5612f54b.

Refs #23663.

This helps with testability of management commands.

Thanks to trac username daveoncode for the report and to
Tim Graham and Claude Paroz for the reviews.

Refs #23685.

Fixed a regression introduced by 28efafa2.
Thanks Michal Čihař for the report and initial patch, and
Collin Anderson and Tim Graham for the reviews.

This commit reverts 67d7da5f.

The previous fix changed the environment globally, which meant
that any call to `call_command(no_color=True)` prevented further
`call_command` with color.

This fix still relies on the environment because it's currently the only
way to reach WSGIRequestHandler, but it's now limited to the `runserver`
command. This seems an acceptable compromise considering `runserver` runs
indefinitely.

Thanks Tim Graham for the review.

This fixes a regression introduced by 2a31d009.
Thanks tony-zhu for the report.

Thanks Baptiste Mispelon for the report.

Thanks Paul Dejean for the report.

Thanks Naddiseo for reporting.

Thanks Aymeric Augustin for review.

This reverts commit 8d6e1afe.
call_command now always set skip_checks to True (tested in
user_commands).

Thanks Loic Bistuer for the report/review and Tim Graham for the
review.

`cache.tests.TestEtagWithAdmin` loaded views from the `admin_views` test
package. This is problematic because when the `cache` test package is
run in isolation, `admin_views` isn't in INSTALLED_APPS, and therefore
loading its models isn't allowed since the app loading refactor.

Overriding execute() bypasses the system check framework among other things.

Fixed a typo in urlencode documentation.