Tickets are entries in the MIT Kerberos RT bug tracking system. To log into RT, go to http://krbdev.mit.edu/rt/ . Committers should be able to log in using certificates using https://krbdev.mit.ed/rt/. Others can log in with username guest and password guest.
To report a bug send mail to firstname.lastname@example.org.
Tickets can be manipulated when committing changes to Subversion; see Manipulating RT tickets using commits for details.