When saving a page:
action=submit TypeError from line 60 of extensions/GoogleAppEngine/job/JobQueueGAE.php: Argument 1 passed to JobQueueGAE::convertJobToTask() must be an instance of Job, instance of JobSpecification given, called in extensions/GoogleAppEngine/job/JobQueueGAE.php on line 36
Reproducible by installing the extension then trying to save a page. Or with Quibble : ZUUL_PROJECT=mediawiki/extensions/GoogleAppEngine quibble --run=selenium.
Fixed by https://gerrit.wikimedia.org/r/437259
Then a page fails to load with Call to undefined function google\net\bccomp() ( https://github.com/GoogleCloudPlatform/appengine-php-sdk/issues/15 ) which is due to the Quibble image lacking the PHP bcmath extension.
Fixed by adding bcmath https://gerrit.wikimedia.org/r/442338