Checks the arguments and options.

    :param args: an object containing the options and arguments of the program.

    :type args: :py:class:`argparse.Namespace`

    :returns: ``True`` if everything was OK.

    If there is a problem with an option, an exception is raised using the
    :py:class:`ProgramError` class, a message is printed to the
    :class:`sys.stderr` and the program exits with error code 1.

def check_args(args):
    """Checks the arguments and options.

    :param args: an object containing the options and arguments of the program.

    :type args: :py:class:`argparse.Namespace`

    :returns: ``True`` if everything was OK.

    If there is a problem with an option, an exception is raised using the
    :py:class:`ProgramError` class, a message is printed to the
    :class:`sys.stderr` and the program exits with error code 1.

    """
    # Checking that the input file exists
    if not os.path.isfile(args.evec):
        m = "{}: no such file".format(args.evec)
        raise ProgramError(m)
    return True