Add helpful error message when a program is terminated by a (Unix) signal, such as a segfault

[mr-c]

Currently one gets a error as the expected outputs are not available, which is technically true but unhelpful.

• Add helpful error message for return code 139
• Add a test for this behaviour

Thanks to @gijzelaerr for the idea

[mr-c]

In general we should emphasis failing return codes over missing outputs, so there may be additional work to do here

[mr-c]

A good start would be adding a _logging.debug entry for the value of the return code in

cwltool/cwltool/job.py

Line 346 in 352daf6

if rcode in self.successCodes:

[gmloose]

I think the title should be changed to "Add helpful error message when a program is terminated by a (Unix) signal", to make it more generic than just catching segmentation faults.

[gmloose]

Who or what sets self.successCodes, self.temporaryFailCodes, and self.permanentFailCodes? I can see these are set in lines 967-969 of command_line_tool.py, using self.tool.get(), and I see that self.tool is assigned a toolpath_object in line 586 of process.py, but then I'm lost because toolpath_object can be one of many objects.

[mr-c]

@gmloose they come from the CWL CommandLineTool description: https://www.commonwl.org/v1.0/CommandLineTool.html#CommandLineTool