ENH,UBY: pyline.main(output=None)

[westurner]

When working with the pyline.pyline.main() function, it's often not necessary to print the results (e.g. when they're appended to to results and the utilized in a downstream function);
there should be a way to not write to stdout or stderr (or a stringio.StringIO (Python 2), io.StringIO).

solution:

With NotImplemented as a default value

• def pyline(output=NotImplemented)
• if not output:
  • don't write sys.stdout
• elif output is NotImplemented:
  • write to sys.stdout (by default)

workaround:

• output=sys.stderr
• output=io.StringIO