Add the first small test for the ErrorProxy
Add the first small test for the ErrorProxy

Others should follow later, but let's start with this most simple one that
verifies the very basic functionality.

rhinstaller/libblockdev,vpodzime/libblockdev,rhinstaller/libblockdev,rhinstaller/libblockdev,vpodzime/libblockdev,atodorov/libblockdev,atodorov/libblockdev,atodorov/libblockdev,vpodzime/libblockdev