upgrade to isort5 (#4399)

* Imports are no longer moved to top.
* `seed-isort-config` is no longer needed.
* Has a `black`-compatible profile/config.
* Also `isorts` the imports anywhere in the code
  (not just at the top).

Also bumps `restyled-isort` to newest version

tests/utils/httpd.py

@@ -16,8 +16,8 @@ class TestRequestHandler(RangeRequestHandler):
         super().__init__(*args, **kwargs)
 
     def translate_path(self, path):
-        import urllib
         import posixpath
+        import urllib
 
         # NOTE: `directory` was introduced in 3.7
         if sys.version_info >= (3, 7):