Unit test module can't be added

Add cmd.test_dummy module under murano/tests/unit and then executed tox, Error log is the following:

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Failed 1 tests - output below:
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unittest2.loader._FailedTest.cmd.test_dummy
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Captured traceback:
~~~~~~~~~~~~~~~~~~~
    Traceback (most recent call last):
    ImportError: Failed to import test module: cmd.test_dummy
    Traceback (most recent call last):
      File "/home/hid-nakamura/murano/.tox/py27/local/lib/python2.7/site-packages/unittest2/loader.py", line 456, in _find_test_path
        module = self._get_module_from_name(name)
      File "/home/hid-nakamura/murano/.tox/py27/local/lib/python2.7/site-packages/unittest2/loader.py", line 395, in _get_module_from_name
        __import__(name)
    ImportError: No module named test_dummy