get variable from variables_mapping.

    Args:
        variable_name (str): variable name
        variables_mapping (dict): variables mapping

    Returns:
        mapping variable value.

    Raises:
        exceptions.VariableNotFound: variable is not found.

def get_mapping_variable(variable_name, variables_mapping):
    """ get variable from variables_mapping.

    Args:
        variable_name (str): variable name
        variables_mapping (dict): variables mapping

    Returns:
        mapping variable value.

    Raises:
        exceptions.VariableNotFound: variable is not found.

    """
    try:
        return variables_mapping[variable_name]
    except KeyError:
        raise exceptions.VariableNotFound("{} is not found.".format(variable_name))