'Update progressbar with an increment.
Parameters
increment_value : int
Value of the increment of process.  The percent of the progressbar
will be computed as
(self.cur_value + increment_value / max_value) * 100
mesg : str
Message to display to the right of the progressbar.  If None, the
last message provided will be used.  To clear the current message,
pass a null string, \'\'.'

def update_with_increment_value(self, increment_value, mesg=None):

    self.cur_value += increment_value
    self.update(self.cur_value, mesg)
