Test failure on Python 3.9

[nijel]

Describe the bug

Test failure on Python 3.9:

 ======================================================================
FAIL: test_lang_code_double (weblate.trans.tests.test_component.ComponentValidationTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/runner/work/weblate/weblate/weblate/trans/tests/test_component.py", line 774, in test_lang_code_double
    self.assertEqual(
AssertionError: 'pt/resources/MessagesBundle_' != 'pt_BR'
- pt/resources/MessagesBundle_
+ pt_BR

To Reproduce

Run tests on Python 3.9

Additional context

https://github.com/WeblateOrg/weblate/runs/1242618490?check_suite_focus=true

[github-actions]

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[nijel]

Caused by changed fnmatch behavior introduced in Python 3.9 via python/cpython#19908.