saltstack/salt — pull request #5819 by terminalmage (2013-06-28 22:48:22+00:00)
Title: Fix traceback on non-yum systems

3b8b6de added yum.rpmtrans.RPMBaseCallback as a base class for
the _YumLogger class, which causes tracebacks on non-yum systems. This
commit fixes that by only creating this class if the yum python
interface is successfully imported.