mypy: add "Optional" to attributes with allowed None
mypy: add "Optional" to attributes with allowed None

These attributes are also used with None value

Signed-off-by: Martin Basti <388356a3851efe39ff0604de6d8fb2e16e10a0b7@redhat.com>

projectatomic/atomic-reactor,fr34k8/atomic-reactor,projectatomic/atomic-reactor,fr34k8/atomic-reactor