FileSystemStorage._save() doesn't catch FileExistsError on concurrent os.mkdirs()

[mar77i]

My django tests (ran in --parallel) raised an exception which Django appears to attempt to be dealing with already:

Traceback (most recent call last):
  [...]
  File "[app dir]/models.py", line 56, in create_user
    return self._create_user(email, password, **extra_fields)
  File "[app dir]/models.py", line 50, in _create_user
    user.save(using=self._db)
  File "[app dir]/models.py", line 157, in save
    save=False
  File "[project dir]venv/lib/python3.5/site-packages/django/db/models/fields/files.py", line 87, in save
    self.name = self.storage.save(name, content, max_length=self.field.max_length)
  File "[project dir]venv/lib/python3.5/site-packages/django/core/files/storage.py", line 49, in save
    return self._save(name, content)
  File "[project dir]venv/lib/python3.5/site-packages/django/core/files/storage.py", line 236, in _save
    os.makedirs(directory)
  File "/usr/lib/python3.5/os.py", line 241, in makedirs
    mkdir(name, mode)
FileExistsError: [Errno 17] File exists: '[storage dir]'

Inspecting storage.py showes that os.makedirs() is guarded with a try...except block concerning FileNotFoundError, but apparently, FileExistsError appears to be what that exception handler was supposed to be catching.

[Tim Graham]

It looks like my mistake in 632c4ffd9cb1da273303bcd8005fff216506c795. We can add a test by mocking os.makedirs to raise FileExistsError.

[Srinivas Reddy Thatiparthy]

Vishvajit ,

Are your working on a fix?

[Tim Graham]

I created a ​PR so we can get this fixed in tomorrow's bug fix release.

[Tim Graham <timograham@…>]

In 98ef3829:

Fixed #29890 -- Fixed FileSystemStorage crash if concurrent saves try to create the same directory.

Regression in 632c4ffd9cb1da273303bcd8005fff216506c795.

[Tim Graham <timograham@…>]

In cd7d6c8a:

[2.1.x] Fixed #29890 -- Fixed FileSystemStorage crash if concurrent saves try to create the same directory.

Regression in 632c4ffd9cb1da273303bcd8005fff216506c795.

Backport of 98ef3829e96ebc73d4d446f92465e671ff520d2b from master.