Comment 10 for bug 1810213

I just noticed that my copy/paste of the error was from when I was using Python 3.5, but the same error is returned with Python 3.7.3:

(openstack) flavor list
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/cmd2/cmd2.py", line 1804, in onecmd_plus_hooks
    statement = self.precmd(statement)
  File "/usr/local/lib/python3.7/site-packages/cliff/interactive.py", line 172, in precmd
    statement.command = cmd_name
  File "/usr/local/lib/python3.7/site-packages/attr/_make.py", line 428, in _frozen_setattrs
    raise FrozenInstanceError()
attr.exceptions.FrozenInstanceError
EXCEPTION of type 'FrozenInstanceError' occurred with message: ''