Enable some more mypy checks

Author: dnicolodi

mypy.ini

@@ -5,8 +5,7 @@ show_traceback = True
 warn_redundant_casts = True
 warn_unused_configs = True
 warn_unused_ignores = True
-; Enabling this will fail on subclasses of untyped imports, e.g. pkginfo
-; disallow_subclassing_any = True
+disallow_subclassing_any = True
 disallow_any_generics = True
 disallow_untyped_calls = True
 disallow_untyped_defs = True