LOCALE_PATHS should be a tuple

[Tim Shaffer]

I was trying to track down why my project was not auto-reloading when files were changed using the dev server.

Turns out, it was an improperly configured LOCALE_PATHS setting. My LOCALE_PATHS was configured like this:

LOCALE_PATHS = (
    '/path/to/locale'
)

Which is actually a string and not a tuple since it does not have a trailing comma. This causes a problem in the autoloader, here:

​https://github.com/django/django/blob/master/django/utils/autoreload.py#L98

Since LOCALE_PATHS is a string, calling basedirs.extend(LOCALE_PATHS) actually causes every character in the string to get appended to basedirs. Then it walks through the tree and tries to find .mo files. And since there are 3 slashes in the string, the autoloader attempts to search the root drive 3 times.

Bottom line is that having LOCALE_PATHS set to a string with slashes causes autoreloading to silently stop working while it attempts to search the entire root drive.

This patch adds LOCALE_PATHS to the list of tuple_settings which checks to make sure it's a tuple.

[Tim Graham]

Needs a test.

[Tim Shaffer]

I didn't see a test for either of the two other settings that were in the tuple_settings list, so I created a new test case in settings_tests.

Should be trivial to duplicate this test to make it work for the other 2 settings as well. I can go ahead and do that too if it's necessary.

[Claude Paroz <claude@…>]

In a1c6cd6a167f90fc4dfd76b2a2de87bc617b26e6:

Fixed #22780 -- Checked that LOCALE_PATHS is really a tuple