stricter mypy settings

Committed via https://github.com/asottile/all-repos

setup.cfg

@@ -53,6 +53,8 @@ disallow_any_generics = true
 disallow_incomplete_defs = true
 disallow_untyped_defs = true
 no_implicit_optional = true
+warn_redundant_casts = true
+warn_unused_ignores = true
 
 [mypy-testing.*]
 disallow_untyped_defs = false