def format_params_diff(parameter_diff):
    """Handles the formatting of differences in parameters.

    Args:
        parameter_diff (list): A list of DictValues detailing the
            differences between two dicts returned by
            :func:`stacker.actions.diff.diff_dictionaries`
    Returns:
        string: A formatted string that represents a parameter diff
    """

    params_output = '\n'.join([line for v in parameter_diff
                               for line in v.changes()])
    return """--- Old Parameters
+++ New Parameters
******************
%s\n""" % params_output