'NoneType' object has no attribute 'write'

[mimitche]

Any idea why I'm getting the following?

laptop:etching-master mike$ python ControlScripts/control.py /dev/cu.usbmodem14201

d 5
Traceback (most recent call last):
File "ControlScripts/control.py", line 198, in
main()
File "ControlScripts/control.py", line 186, in main
cmdVector(idx, int(steps), (idx+2)%len(DIR_TO_INDEX), 0)
File "ControlScripts/control.py", line 139, in cmdVector
_dumbCmdVector(horizontal[0], horizontal[1], vertical[0], vertical[1])
File "ControlScripts/control.py", line 101, in _dumbCmdVector
ser.write("v")
AttributeError: 'NoneType' object has no attribute 'write'