Sorry if I'm not conforming right place (I saw this
https://github.com/nicferrier/emacs-contributor-guide#testing, so I thought
it's ok to discuss new flymake's bug)

How to reproduce:
1. open emacs with -Q option
2. on scratch buffer, invoke M-x flymake-mode
3. C-x 3, and then C-x b return (switched message buffer)
4. edit something on scratch buffer
5. and then immediately switch to another buffer (I used C-x o and then
switch message buffer by opend at 3)
6. got `error in process sentinel: Invalid function: flymake-log` on
message buffer

Thanks
Yuta Yamada