tests / scripts: blacken and isort (#4704)

I often run black and isort in typeshed root and then have to undo these
changes.

Co-authored-by: hauntsaninja <>

tests/mypy_selftest.py

@@ -1,10 +1,10 @@
 #!/usr/bin/env python3
 """Script to run mypy against its own code base."""
 
-from pathlib import Path
 import subprocess
 import sys
 import tempfile
+from pathlib import Path
 
 MYPY_VERSION = "0.790"