Traceback (most recent call last):
  File "C:\Users\me\PycharmProjects\f\venv\lib\site-packages\matplotlib\cbook.py", line 298, in process
    func(*args, **kwargs)
  File "C:\Users\me\PycharmProjects\f\venv\lib\site-packages\control\pzmap.py", line 470, in _click_dispatcher
    K, s = _find_root_locus_gain(event, sys, ax)
  File "C:\Users\me\PycharmProjects\f\venv\lib\site-packages\control\pzmap.py", line 531, in _find_root_locus_gain
    return None, s
UnboundLocalError: local variable 's' referenced before assignment