We need:
1. Ticket/PR for 3.0 to add a note/warning.
2. Ticket/PR for 3.1 to add an install check/whatever other checks we already have for 5.3 and refuse to install if it is not met. Note that we have the acp environment checks PR fixed and waiting for another review pass, it would be great to review that one and test it with the 5.2 to 5.3 bump.
3. Announcement on .com, is that Nils' prerogative or can anyone make it? What is the procedure for that?
4. Events PR redone to copy paste symfony verbatim and/or vendor it.




