#552 Detector non-linearity and reciprocity failure

A basic method to apply any desired non-linearity on an Image has been included to begin with. The non-linearity can be specified by a LookupTable or as a function, possibly with parameters, that can act on NumPy arrays. In addition, it also includes a feature to correct for reciprocity failure. A basic unit test to test these functionalities have also been built.
>So Jim recommended (and I agree) to pretty much never catch an exception just to repackage it with a new message and rethrow. Just let the original exception go with the full trace up to a point where someone may be able to appropriately deal with it.

I can see the logic in that, and stand corrected.  It's less aesthetically pleasing to not repackage the error and the full trace will confuse Python beginners more than a simpler, more descriptive message, but it's true that the repackaging of exceptions destroys possibly useful information in the full trace. I think it depends who your target users are, but for GalSim it's fine to assume ones with a basic minimum level of experience.