Fix uses of Mock.assert_called_once in unit tests (fixes OPS-2077)
Serve error page content with the same protocol as the page itself (fixes OPS-2039)
Merge pull request #25 from olivierlefloch/olefloch/OPS-2039/fix_mixed_content_on_error_pages

OPS-2039 - Serve CSS and images on error page with proper protocol
Merge pull request #24 from olivierlefloch/olefloch/OPS-2077/fix_mock_assert_called

Fix uses of Mock.assert_called_once in unit tests (fixes OPS-2077)