video/tools/drawing.py local variable 'norm' referenced before assignment

[liikii]

There seems to be a bug

File "/home/debian2/anaconda3/lib/python3.7/site-packages/moviepy-2.0.0.dev1-py3.7.egg/moviepy/video/tools/drawing.py", line 156, in color_gradient
    n_vec = vector / norm ** 2  # norm 1/norm(vector)
UnboundLocalError: local variable 'norm' referenced before assignment

[tburrows13]

Thank you for the report. This is my fault: in #1101, the line if vector is not None: was incorrectly changed to if vector:, which caused #1205. Then I tried to fix it in #1212 but I apparently missed the not, so the logic is faulty. You can fix it in your installation by adding the not to that line: https://github.com/Zulko/moviepy/blob/master/moviepy/video/tools/drawing.py#L149

[tburrows13]

Fixed in ff15fcf