Seen for example on https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CommentStreams/+/718752:
PHP Deprecated: Hook userCan was deprecated in MediaWiki 1.37 but is registered in /workspace/src/extensions/CommentStreams/extension.json
Seen for example on https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CommentStreams/+/718752:
PHP Deprecated: Hook userCan was deprecated in MediaWiki 1.37 but is registered in /workspace/src/extensions/CommentStreams/extension.json
Thank you for reporting this! It has been fixed in https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CommentStreams/+/709101.