buildout fails with string endoding exception if gmusicapi is installed

Tried to run buildout to set up python-etcd. Got the following exception:

$ bin/buildout -D
Develop: '/home/shaun/git/python-etcd/.'
While:
  Installing.
Traceback (most recent call last):
  File "/home/shaun/git/python-etcd/eggs/zc.buildout-2.3.1-py2.7.egg/zc/buildout/buildout.py", line 1946, in main
    getattr(buildout, command)(args)
  File "/home/shaun/git/python-etcd/eggs/zc.buildout-2.3.1-py2.7.egg/zc/buildout/buildout.py", line 525, in install
    self._compute_part_signatures(install_parts)
  File "/home/shaun/git/python-etcd/eggs/zc.buildout-2.3.1-py2.7.egg/zc/buildout/buildout.py", line 770, in _compute_part_signatures
    sig = _dists_sig(pkg_resources.working_set.resolve([req]))
  File "/home/shaun/git/python-etcd/eggs/zc.buildout-2.3.1-py2.7.egg/zc/buildout/buildout.py", line 1637, in _dists_sig
    result.append(dist.project_name + '-' + _dir_hash(location))
  File "/home/shaun/git/python-etcd/eggs/zc.buildout-2.3.1-py2.7.egg/zc/buildout/buildout.py", line 1606, in _dir_hash
    hash.update(' '.join(filenames).encode())
UnicodeDecodeError: 'ascii' codec can't decode byte 0xed in position 176: ordinal not in range(128)
(Pdb) locals().keys()
['dir_hash', 'sname', 'hash', 'name', 'f', 'data', 'filenames', 'dirpath', 'path', 'dirnames', 'sections', 'dir']
(Pdb) name
'webclient.py'
(Pdb) dirpath
'/usr/local/lib/python2.7/dist-packages/gmusicapi/test'

Turned out to be gmusicapi, which includes a file with non-ascii unicode characters in the name.