Log Message:
py-mutagen: updated to 1.39

1.39:
* Tests:
  * Require `hypothesis <https://hypothesis.readthedocs.io>`__
  * Run pycodestyle/pyflakes tests by default. Skip with ``--no-quality`` or
    ``-m no quality`` when using pytest directly.
* Python 3.3 is no longer supported
* MP3: Improved bitrate accuracy for files with XING header
* ASF: Fix case where some tags resulted in broken ASFUnicodeAttribute
  instances
* Add support for filesystems which don't support opening files read/write
  (gvfs over fuse for example)
* mid3v2: Add support for USLT
* Minor improvements