add a cwl-runner error code for validation failure

[mr-c]

https://github.com/common-workflow-language/cwl-v1.2/blob/main/cwl-runner.cwl#L56

[mr-c]

Consider also adding https://github.com/IBMSpectrumComputing/cwlexec#exit-code-definition

Exit Code	Description
0	The workflow is done
33	There is an unsupported feature in the workflow
130	User used Ctrl + C to interupt the workflow
250	The workflow input/output cannot be found
251	Fail to parse workflow
252	Fail to load workflow inputs
253	Fail to evaluate the expression in workflow
254	Fail to capture the workflow/step output after the workflow/step is done
255	System exception. For example, command arguments are wrong; the CWL workflow description file cannot be found; bsub/bwait command cannot be found

@tetron What do you think of these exit codes for the cwl-runner interface?

[tetron]

Sure, that seems like a good idea. We would want to adjust cwltool to emit them. Would "validation error" be code 251 in this scheme?

[mr-c]

Would "validation error" be code 251 in this scheme?

Do you want to distinguish between bad YAML/JSON and other errors? If so then we need separate exit codes, otherwise that would all be 251, yep.