https://github.com/jazzband/contextlib2/issues/53

--- contextlib2-21.6.0.orig/dev/mypy.allowlist
+++ contextlib2-21.6.0/dev/mypy.allowlist
@@ -0,0 +1,3 @@
+# Deprecated APIs that never graduated to the standard library
+contextlib2.ContextDecorator.refresh_cm
+contextlib2.ContextStack