refactor(mirror_project_in): address 'flake8' findings
files/mirror_project_in.py:6:1: F401 'datetime.datetime' imported but unused
files/mirror_project_in.py:6:1: F401 'datetime.timedelta' imported but unused
files/mirror_project_in.py:8:1: F401 'sqlalchemy.exc.SQLAlchemyError' imported but unused
files/mirror_project_in.py:31:45: E711 comparison to None should be 'if cond is not None:'
files/mirror_project_in.py:50:80: E501 line too long (82 > 79 characters)