Next Frame Prediction functions.gcd deprecation

[JohnENoonan]

Hello, issues don't seem to be enabled on the pix2pixHD fork so I hope it is ok to write here. functions.gcd(a,b) has been deprecated and I just encountered an error when running. The lines https://github.com/dvschultz/pix2pixHD/blob/video/train_video.py#L10-L11 can be updated to:

import math
def lcm(a,b): return abs(a * b)/math.gcd(a,b) if a and b else 0

Thank you for this awesome resource!