I installed from http://download.moodle.org/plugins/mod/certificate.zip, and I am not sure if this is the same as HEAD
installtion was ok, but I got

Capability "mod/certificate:view" was not found! This should be fixed in code.

• line 579 of /lib/accesslib.php: call to debugging()
• line 1026 of /lib/accesslib.php: call to has_capability()
• line 22 of /mod/certificate/view.php: call to require_capability()

same with review.php