Code review comment for lp:~mwilck/duplicity/duplicity

'$ tox' yields the following:

======================================================================
FAIL: test_dirx (testing.functional.test_rdiffdir.RdiffdirTest)
Test cycle on testfiles/dirx
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Traceback (most recent call last):
  File "/Users/ken/workspace/duplicity-src8/testing/functional/test_rdiffdir.py", line 88, in test_dirx
    'testfiles/empty_dir'])
  File "/Users/ken/workspace/duplicity-src8/testing/functional/test_rdiffdir.py", line 50, in run_cycle
    self.run_rdiffdir("sig %s %s" % (seq_path.name, sig_path.name))
  File "/Users/ken/workspace/duplicity-src8/testing/functional/test_rdiffdir.py", line 37, in run_rdiffdir
    self.run_cmd("rdiffdir " + argstring)
  File "/Users/ken/workspace/duplicity-src8/testing/functional/test_rdiffdir.py", line 33, in run_cmd
    assert not os.system(command)
AssertionError