Raise more informative error when no outputs are found

[julianhess]

Current, if no outputs are found, the only clue is this getting printed to stdout:

Expecting value: line 1 column 1 (char 0)

presumably from delocalizer.py.

We need to make output-related error messages clearer.

[agraubert]

This gets printed to a job's stdout and not the terminal, right?

[julianhess]

Correct.

[julianhess]

If the main script exits with nonzero status, we don't want this to be clobbered by a nonzero delocalizer.py exit.

Thus, delocalizer.py should only exit 1 if the script exited 0; otherwise, it should pass through the script's nonzero exit code.

It should write an informative message to stderr. Furthermore, localizer.delocalize() should also pick up on this error and write something to the Canine console output.