Paver: fail if pylint/pep8 violations threshold is breached.

Ok this will take some work.

Perhaps something akin to what the Jenkins plugin is parsing: https://github.com/jenkinsci/violations-plugin/blob/d5b4d6d7cd4cafa5e253be6abe3f2f3d27ab90cd/src/main/java/hudson/plugins/violations/types/pylint/PyLintParser.java