Use Python 3.9 for mypy self check (#10362)

srittau · web-flow · commit 0603ae44f3a3 · 2021-04-23T08:35:03.000-07:00
Using obsolete Python 3.5 breaks typeshed's execution of mypy's self
check, as typeshed does not support Python 3.5 anymore.
diff --git a/mypy_self_check.ini b/mypy_self_check.ini
@@ -18,5 +18,5 @@ show_error_codes = True
 pretty = True
 always_false = MYPYC
 plugins = misc/proper_plugin.py
-python_version = 3.5
+python_version = 3.9
 exclude = /mypy/typeshed/
