repo: Fix warnings reported by flake8

  repo:342:5: E306 expected 1 blank line before a nested definition, found 0
  repo:617:5: F841 local variable 'ret' is assigned to but never used

Change-Id: I364fdb5dac8ebaff398b848935fe8356cb9ed2d3
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/255035
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: David Pursehouse <dpursehouse@collab.net>