isort: format codebase

Change-Id: I6f11d123b68fd077f558d3c21349c55c5f251019
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/383715
Reviewed-by: Gavin Mak <gavinmak@google.com>
Tested-by: Mike Frysinger <vapier@google.com>
Commit-Queue: Mike Frysinger <vapier@google.com>

tests/test_git_superproject.py

@@ -21,10 +21,11 @@ import tempfile
 import unittest
 from unittest import mock
 
+from test_manifest_xml import sort_attributes
+
 import git_superproject
 import git_trace2_event_log
 import manifest_xml
-from test_manifest_xml import sort_attributes
 
 
 class SuperprojectTestCase(unittest.TestCase):