sidereal.py: Internal maintenance specification

# - - -   u s a g e

def usage ( *L ):
    """Print a usage message and stop.

      [ L is a list of strings ->
          sys.stderr  +:=  (usage message) + (elements of L,
                           concatenated)
          stop execution ]
    """
    print >>sys.stderr, "*** Usage:"
    print >>sys.stderr, "***   aard az+alt lat lon datetime"
    print >>sys.stderr, "*** Error: %s" % "".join(L)
    raise SystemExit