Don't lose AttributeError in API Wrappers

Instead of (implicitly) catching the AttributeError, and later
creating and raising a new one, we just re-raise the original
exception. This way all the information from the original is
retained, including the name of the actual object on which it
happened.

Change-Id: Idc0c5a8ed5dfca6a8724e393c220baf9960564ed
Closes-bug: #1274097
Merge "Don't lose AttributeError in API Wrappers"