Use sanity instead of assert in the fake plugin
The sanity function produces a log message when it fails, which may help us discover why we are getting SIGABRT in the fake plugin.
Related to https://redmine-old.labs.nic.cz/issues/4136.
The sanity function produces a log message when it fails, which may help us discover why we are getting SIGABRT in the fake plugin.
Related to https://redmine-old.labs.nic.cz/issues/4136.