Bug 14807

The code in meta/classes/image.bbclass do_image_qa indicates that image QA checks should raise oe.utils.ImageQAFailed exceptions when a problem is discovered.  

When the actual test function is executed by bb.utils.better_exec, there is no special handling for ImageQAFailed and better_exec will print the backtrace before forwarding the exception to do_image_qa to print the expected error messages. 

It's worth noting that the only image_qa_test in Poky -- license_qa_dead_symlink from meta/classes/license_image.bbclass -- does not use ImageQAException.  It uses bb.error instead.

The best solution might be to migrate to the oe.qa.handle_error function, except it might break existing image qa checks in other layers. 

Making ImageQAFailed inherit from BBHandledException would make better_exec ignore it.  But that would mean importing bb.utils into oe.utils which currently only imports standard library modules.  

Making better_exec aware of ImageQAFailed would reverse the import problem and better_exec should not need to know about image_qa specifics.

A more pythonic option might be to implement some kind of protocol where we make Exceptions indicate their bbhandled status with a object property somehow.