The following file(s) added utf-8 encoding but never used. So we can
remove them at all.
os_api_ref/tests/test_warnings.py
os_api_ref/tests/test_os_api_ref.py
os_api_ref/tests/test_microversions.py
os_api_ref/tests/test_basic_example.py
os_api_ref/tests/base.py
os_api_ref/__init__.py
Change-Id: If08e1b00f777a146e2c582f5a194e022a215066e