This causes non-local side effects that are hard to track down. E.g:

--- import errors ---
Failed to import test module: tests.test_merge_yaml
Traceback (most recent call last):
  File "/home/will/.pyenv/versions/3.7.7/lib/python3.7/unittest/loader.py", line 436, in _find_test_path
    module = self._get_module_from_name(name)
  File "/home/will/.pyenv/versions/3.7.7/lib/python3.7/unittest/loader.py", line 377, in _get_module_from_name
    __import__(name)
  File "/home/will/code/kolla-ansible/tests/test_merge_yaml.py", line 19, in <module>
    from ansible.errors import AnsibleModuleError
ModuleNotFoundError: No module named 'ansible.errors'; 'ansible' is not a package

This `'ansible' is not a package` message occurs because ansible is a Mock.

Depends-On: https://review.opendev.org/#/c/726768/
Change-Id: Iddbdd3d855daadbf12536cc990559e6b8e123051