Code review comment for ~ilasc/launchpad:bug-1910403

If however we do have the Maintainer email address in the changes file and add a non ASCII character in the email template params, we see this failure stack, again associated with failing to verify the signature:

processChangesFile, uploadprocessor.py:409
processUpload, test_uploadprocessor.py:337
testUploadWithoutMaintainerEmail, test_uploadprocessor.py:553
_run_test_method, testcase.py:723
_run_user, runtest.py:191
_run_core, runtest.py:144
_run_prepared_result, runtest.py:108
_run_one, runtest.py:94
run, runtest.py:80
run, testcase.py:675
__call__, case.py:673
run_tests, runner.py:396
run_layer, runner.py:474
run_tests, runner.py:293
run, runner.py:191
main, test.py:275
<module>, test:8