Port _SixMetaPathImporter to Python 3.10. (#343)

Fixes #341.

Co-authored-by: Benjamin Peterson <benjamin@python.org>

Author: vstinner

six.py

@@ -223,6 +223,12 @@ def get_code(self, fullname):
         return None
     get_source = get_code  # same as get_code
 
+    def create_module(self, spec):
+        return self.load_module(spec.name)
+
+    def exec_module(self, module):
+        pass
+
 _importer = _SixMetaPathImporter(__name__)