Adjust imports for 3.10

Author: encukou

Lib/test/test_posixpath.py

@@ -1,4 +1,5 @@
 import os
+import sys
 import posixpath
 import unittest
 from functools import partial

Lib/test/test_tarfile.py

@@ -3328,7 +3328,7 @@ def check_context(self, tar, filter, *, check_flag=True, ignored_trees=()):
                 self.expected_paths = set()
             else:
                 for ignored_tree in ignored_trees:
-                    os_helper.rmtree((self.destdir / ignored_tree).resolve())
+                    support.rmtree((self.destdir / ignored_tree).resolve())
                 self.raised_exception = None
                 self.reraise_exception = False
                 self.expected_paths = set(self.outerdir.glob('**/*'))