Magic Folder tests: ascii decode error with Twisted 15.0.0

[zooko]

Magic Folder 'client-0' uploader: stop
'magic_folder.uploader.dirs_monitored' += -1
Traceback (most recent call last):
  File "/home/zooko/playground/tahoe/tahoe-lafs/src/allmydata/test/test_magic_folder.py", line 55, in _wait_until_started
    return self.magicfolder.ready()
  File "/home/zooko/playground/tahoe/tahoe-lafs/src/allmydata/frontends/magic_folder.py", line 80, in ready
    d = self.uploader.start_scanning()
  File "/home/zooko/playground/tahoe/tahoe-lafs/src/allmydata/frontends/magic_folder.py", line 226, in start_scanning
    d = self._scan(u"")
  File "/home/zooko/playground/tahoe/tahoe-lafs/src/allmydata/frontends/magic_folder.py", line 238, in _scan
    fp = self._get_filepath(reldir_u)
  File "/home/zooko/playground/tahoe/tahoe-lafs/src/allmydata/frontends/magic_folder.py", line 123, in _get_filepath
    return extend_filepath(self._local_filepath, relpath_u.split(u"/"))
  File "/home/zooko/playground/tahoe/tahoe-lafs/src/allmydata/util/encodingutil.py", line 265, in extend_filepath
    fp = fp.child(segment)
  File "/usr/local/lib/python2.7/dist-packages/Twisted-15.0.0-py2.7-linux-x86_64.egg/twisted/python/filepath.py", line 696, in child
    newpath = abspath(joinpath(self.path, norm))
  File "/usr/lib/python2.7/posixpath.py", line 80, in join
    path += '/' + b
exceptions.UnicodeDecodeError: 'ascii' codec can't decode byte 0xc4 in position 127: ordinal not in range(128)

<daira> zooko: force Twisted to be >= 15.2.0
<daira> that'll work around the problem

[zooko]

Upgrading to Twisted trunk (which identifies itself as "Twisted 15.4.0") fixed it.

[daira]

This is fixed on the 2438.magic-folder-stable.5 branch, by declaring a dependency on Twisted >= 15.2.0.