The libregrtest change looks good but I disagree on the pty/openpty changes. If you look at all the current Linux man pages and documentation, they follow the master/slave terminology. Generally, Python documentation for underlying os functions like fork, stat etc are kept short because the OS documentation is the ultimate resource for them. 

This change causes a deviation from the existing standard and will only serve to make things more confusing, I would suggest deferring it until the actual OS documentation reflects this change as well.