Adds more error checking in pytracer.c
Adds more error checking in pytracer.c

JosuaKrause/reprozip,ViDA-NYU/reprozip,ViDA-NYU/reprozip,ViDA-NYU/reprozip,JosuaKrause/reprozip,ViDA-NYU/reprozip,JosuaKrause/reprozip,ViDA-NYU/reprozip,JosuaKrause/reprozip