Exclude mypy on Python 3.10 as workaround for python/typed_ast#156.

Author: jaraco

setup.cfg

@@ -38,7 +38,8 @@ testing =
 	pytest-black >= 0.3.7; python_implementation != "PyPy"
 	pytest-cov
 	# python_implementation: workaround for jaraco/skeleton#22
-	pytest-mypy; python_implementation != "PyPy"
+	# python_version: workaround for python/typed_ast#156
+	pytest-mypy; python_implementation != "PyPy" and python_version < "3.10"
 	pytest-enabler
 
 	# local