Update the old configuration file with new values.

        :param old: old configuration to update.
        :param backup_path: path to write a backup of the old config file.

        :return:

def update(self, old, backup_path=None):
        """
        Update the old configuration file with new values.

        :param old: old configuration to update.
        :param backup_path: path to write a backup of the old config file.

        :return:
        """
        for category in old.params.keys():
            for parameter in old.params[category].keys():
                if (category in self.params and parameter in self.params[category] and
                        (old.params[category][parameter] != self.params[category][parameter]) and
                        (category != "version")):
                    print ("Config value '%s.%s' "
                           "in old configuration is different "
                           "from the new version\n"
                           "[old value] = %s\n"
                           "[new value] = %s"
                           "" % (category, parameter,
                                 old.params[category][parameter],
                                 self.params[category][parameter]))
                    answer = raw_input("Do you want to overwrite? ([y]/n) ")
                    while answer.lower() not in ['y', 'yes', 'n', 'no']:
                        answer = raw_input("Answer not recongnized. Enter 'y' or 'n'. ")

                    if answer in ['n', 'no']:
                        old_value = old.params[category][parameter]
                        self.params[category][parameter] = old_value
                elif not (category in self.params and
                          parameter in self.params[category]):
                    print ("Deprecated config option '%s.%s' has "
                           "been removed." % (category, parameter))
        if backup_path is not None:
            old.write_out_config(backup_path)
            print "Backup saved in %s." % backup_path