This function sends a string to the standard error stream, and also appends it to a cumulative log file.
# - - - m e s s a g e - - -
def message ( text ):
"""Send a message to stderr and ERROR_LOG.
[ text is a string ->
sys.stderr +:= text
file ERROR_LOG +:= text ]
"""
sys.stderr.write ( text )
logFile = open ( ERROR_LOG, "a" )
logFile.write ( text )
logFile.close()