Standard documented name for error callback arguments is "failure" but various other names have been employed in past.
This function provides reverse compatibility by picking the failure callback argument out of a config object
be it named failure, failureCallback or errorCallback.
Standard documented name for error callback arguments is "failure" but various other names have been employed in past. This function provides reverse compatibility by picking the failure callback argument out of a config object be it named failure, failureCallback or errorCallback.