Related Gerrit Patches:
|mediawiki/extensions/Math : master||Add action-purge message to Math extension|
Failing to purge if the purge right is not there doesn't seem right as purge right doesn't actually prevent from purging the cache - it only asks for a confirmation when the user doesn't have this right.
// The effect of loading this page is comparable to purge a page. // If desired a dedicated right e.g. "viewmathstatus" could be used instead.
That seems the right thing to do here.