Error messages should be more helpful

[kweide]

While modifying a testing configuration for debugging, I findflashxtest run-suite failing with error messages like this:

Traceback (most recent call last):
  File "/scratch/jenkins-slave/workspace/Flash-X-debug_GCC/pyenv/lib/python3.8/site-packages/FlashXTest/lib/info.py", line 132, in jobListFromNode
    if infoNode.subNodes:
AttributeError: 'NoneType' object has no attribute 'subNodes'

This appears to happen when a .suite file requests a test that isn't actually defined in the .info file.

This traceback is not helpful in locating the cause of the failure.
At a minimum, the nodeName of the offending requested test should be printed.

[kweide]

Perhaps I got that wrong, and the message was generated already at the flashxtest init stage.
It is still true that the error messages should be more informative - including an indication which command actually failed, so one isn't left wondering (while going through the output of some test job) whether it was flashxtest run-suite or flashxtest init that failed...

[kweide]

Here is another uncaught exception - this one actually happens to mention the offending name, so that is better; but the message could still be friendlier.

Traceback (most recent call last):
  File "/scratch/jenkins-slave/workspace/Flash-X-debug_GCC/pyenv/lib/python3.8/site-packages/FlashXTest/lib/info.py", line 212, in createInfo
    setupInfo = setupYaml[testSpec.setupName][testSpec.nodeName]
KeyError: 'Composite/Sedov/AMR/2dSph/Paramesh/unsplitPLM'