fix for lp712982, and likely a variety of other dashboard error handling  issues.  This fix simply causes the default error code for ApiError to be 'ApiError' rather than 'Unknown', which makes dashboard handle the error gracefully, and makes euca error output slightly prettier
fix for lp712982, and likely a variety of other dashboard error handling 
issues.  This fix simply causes the default error code for ApiError
to be 'ApiError' rather than 'Unknown', which makes dashboard handle
the error gracefully, and makes euca error output slightly prettier

citrix-openstack-build/oslo.versionedobjects,openstack/oslo.versionedobjects