Instead of collecting the full rpmlint output and then printing it to stream (stdout) as a whole, pipe it stream instead, so that the output is displayed in real time and the command doesn't seem to be stuck. That will help us prevent buildbot from killing the task for a very large sets of RPMs, like here:
http://taskotron-dev.fedoraproject.org/taskmaster/builders/x86_64/builds/12666