Don't execute py2rpm with no names.
Don't execute py2rpm with no names.

An error can be triggered by downloading anvil and then
just trying to uninstall (before preparing and installing).

Change-Id: I1e7fa76b55ec23851374966d4b49fcedd648e3d6

mc2014/anvil,stackforge/anvil,mc2014/anvil,stackforge/anvil