Don't check for a file's existence before deleting

[Jon Dufresne]

There are a couple places in Django (file-based cache and FileSystemStorage) that do a file-existence check before removing a file). This leads to an unnecessary race condition. It's easier to simply try to delete the file and pass silently if the file doesn't exist.

​PR

[Tim Graham <timograham@…>]

In 359be1c8:

Fixed #26691 -- Removed checking for a file's existence before deleting.

File operations always raise a ENOENT error when a file doesn't exist.
Checking the file exists before the operation adds a race condition
condition where the file could be removed between operations. As the
operation already raises an error on a missing file, avoid this race and
avoid checking the file exists twice. Instead only check a file exists
by catching the ENOENT error.