Reads a single config file into the parser, silently failing if the file
    does not exist.

    Args:
    parser (ConfigParser): parser to read the file into.
    filepath (str): full path to the config file.

def _read_single(parser, filepath):
    """Reads a single config file into the parser, silently failing if the file
    does not exist.

    Args:
    parser (ConfigParser): parser to read the file into.
    filepath (str): full path to the config file.
    """
    from os import path
    global packages
    if path.isfile(filepath):
        parser.readfp(open(filepath))