mypy self check: exclude test-data (#11258)

So that mypy primer doesn't freak out on #9636

Co-authored-by: hauntsaninja <>

Author: hauntsaninja

mypy_self_check.ini

@@ -19,4 +19,4 @@ pretty = True
 always_false = MYPYC
 plugins = misc/proper_plugin.py
 python_version = 3.6
-exclude = mypy/typeshed/
+exclude = mypy/typeshed/|mypyc/test-data/|mypyc/lib-rt/