commit 4913e8ede09bf6f4efc27d3fb6e224cb87bbb9ee (python-mutagen update)
breaks a test in beets:

...
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FAIL: test_read_audio_properties (test.test_mediafile.AIFFTest)
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Traceback (most recent call last):
  File "/tmp/guix-build-beets-1.4.9.drv-0/beets-1.4.9/test/test_mediafile.py", line 440, in test_read_audio_properties
    self.assertEqual(getattr(mediafile, key), value)
AssertionError: 16 != 0

======================================================================
FAIL: test_read_audio_properties (test.test_mediafile.WavpackTest)
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Traceback (most recent call last):
  File "/tmp/guix-build-beets-1.4.9.drv-0/beets-1.4.9/test/test_mediafile.py", line 440, in test_read_audio_properties
    self.assertEqual(getattr(mediafile, key), value)
AssertionError: 16 != 0

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Ran 1901 tests in 124.212s


guix time-machine --commit=bd994bbb2003f3af936836bbf148660a81a3037b -- build beets
works.