Use a context manager to unregister model field lookups in tests

[Mads Jensen]

There are some places in the test suite that follow this pattern:

try:
   CharField.register_lookup(Length)
   # some test code
finally:
   CharField._unregister_lookup(Length)

It'd be better to use a context manager (addCleanup() was originally proposed) to handle this stuff.

[Srinivas Reddy Thatiparthy]

https://code.djangoproject.com/ticket/29658

[Claude Paroz]

The current patch is using a context manager instead of the try/finally method.
Mads, is that something you are comfortable with, or do you still see some benefit with addCleanup?

[Tim Graham]

Patch looks good to me, unless there's some reason to prefer addCleanup().

[Simon Charette]

Using context managers should be fine as well.

[Tim Graham <timograham@…>]

In 233c70f0:

Fixed #29658 -- Registered model lookups in tests with a context manager.