few unit tests (class TestMasakariAPI) are failing

I installed all requirements and test-requirements modules.
Then I ran unittest using pytest framework but 3 of them are failing and others are passing.

```
$ pytest -k unit

===================================================================================== FAILURES ======================================================================================
_____________________________________________________________________ TestMasakariAPI.test_continues_on_failure _____________________________________________________________________
NOTE: Incompatible Exception Representation, displaying natively:

_StringException: Traceback (most recent call last):
TypeError: test_continues_on_failure() takes exactly 2 arguments (1 given)

_____________________________________________________________________ TestMasakariAPI.test_fails_if_all_failed ______________________________________________________________________
NOTE: Incompatible Exception Representation, displaying natively:

_StringException: Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/mock/mock.py", line 1305, in patched
    return func(*args, **keywargs)
TypeError: test_fails_if_all_failed() takes exactly 3 arguments (2 given)

____________________________________________________________________ TestMasakariAPI.test_fails_if_none_started _____________________________________________________________________
NOTE: Incompatible Exception Representation, displaying natively:

_StringException: Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/mock/mock.py", line 1305, in patched
    return func(*args, **keywargs)
TypeError: test_fails_if_none_started() takes exactly 3 arguments (2 given)

```

Each of them are saying there are extra argument passed to test functions. The extra argument is version_cache whose origin could not be found by me. I tried to remove version_cache from tests then there were further more issues.