'Load a readline history file.'

def read_history_file(self, filename=None):

    if (filename is None):
        filename = self.history_filename
    try:
        for line in open(filename, 'r'):
            self.add_history(lineobj.ReadLineTextBuffer(line.rstrip()))
    except IOError:
        self.history = []
        self.history_cursor = 0
