meshpy reports gmsh failure when warnings occur

[david-zwicker]

The meshpy error processing is a bit too sensitive in that it simply scans for the word 'error' in the stderr of the gmsh output (https://github.com/inducer/meshpy/blob/master/meshpy/gmsh.py#L182). This is problematic if some warning occurs during the gmsh run, which typically leads to output like this:

Warning : ------------------------------
Warning : Mesh generation error summary
Warning : 6 warnings
Warning : 0 errors
Warning : Check the full log for details
Warning : ------------------------------

Clearly, there was no error, but meshpy still throws a GmshError.

[inducer]

I'm open to taking a patch to introduce an option like break_on_warning=True. (i.e. defaulting to true to match current behavior) I'm not sure how one could determine whether an error or a warning occurred--I'm not too fond of parsing the gmsh output, but I suppose that could be done. Another aspect is that I've found that meshes that come out with warnings are most often pretty much unusable--so, at least in part, this behavior is there by design.