Catch all yaml exceptions

Instead of catching 2 specific exceptions, rather catch the generic
YAMLError as the documentation suggests:
http://pyyaml.org/wiki/PyYAMLDocumentation#YAMLError

Closes-bug: #1242155
Change-Id: I840d5eccafcc576d7a0022d81e5bc50af2d77803
Merge "Catch all yaml exceptions"