'Should emit a conventional usage message.'

def test_message_follows_conventional_format(self):

    instance = self.test_instance
    progname = self.test_program_name
    argv = [self.test_program_path]
    expect_stderr_output = ('                                                usage:    %(progname)s    ...\n                                                ' % vars())
    self.failUnlessRaises(SystemExit, instance._usage_exit, argv)
    self.failUnlessOutputCheckerMatch(expect_stderr_output, self.mock_stderr.getvalue())
