This upstream commit https://github.com/facebook/mysql-5.6/commit/8b34f82b403ad2904ff0f6f5bb65cf90bf274fdf introduced a check on create table that throws an error if a FOREIGN KEY constraint is specified during create table. It seems to not check if a new FK constraint is added via ALTER.
This is inconsistent behavior w.r.t. MySAM, Memory, TokuDB, and possibly other engines that ignore and absorb the constraint, leaving the burden of detection on the user.
This also prevents the use of many mtr template type tests such as those in extra/rpl_tests (see