Solved Propper approach if portmaster shows obsolete and unmaintained ports

devel/llvm37 I can't update ports anymore. portmaster complains:
===>>> The devel/llvm37 port has been deleted: Obsolete and unmaintained upstream
===>>> Aborting update
The same message shows devel/llvm37. The is no port directory any more. What should a novice do in such situation?
Find out what depended on it: pkg info -r llvm37. Then rebuild those ports.