Prints the specified message as an error; prepends "ERROR" to
    the message, so that can be left off.

def err(msg, level=-1, prefix=True):
    """Prints the specified message as an error; prepends "ERROR" to
    the message, so that can be left off.
    """
    if will_print(level) or verbosity is None:
        printer(("ERROR: " if prefix else "") + msg, "red")