Test failure in test_terminal

[mithrandi]

[FAIL]
Traceback (most recent call last):
  File "/home/mithrandi/code/Mantissa/xmantissa/test/test_terminal.py", line 274, in test_write
    self.assertIn('some bytessome more', str(terminal))
  File "/home/mithrandi/deployment/virtualenvs/Mantissa/local/lib/python2.7/site-packages/twisted/trial/_synctest.py", line 485, in assertIn
    % (containee, container))
twisted.trial.unittest.FailTest: 'some bytessome more' not in '<xmantissa.test.test_terminal.FakeTerminal instance at 0x7f9a11f42638>'

xmantissa.test.test_terminal.ReturnToMenuTests.test_write

This is caused by https://twistedmatrix.com/trac/ticket/8843 which made it into a release, so we probably need to work around it ourselves.