Phil , if light had mass the effect of gravity would be to draw the light towards the object creating the gravity force, not around it as happens when gravity bends the space/time.
2 links below of Einstein's cross, which explain the situation, and an image of it from a 10"
http://www.astronomynotes.com/relativity/s4.htm
http://voltaire.csun.edu/roland/cross.html
Einstein's Cross with an AP 10 inch f/14.6 Maksutov-Cassegrain
The gravity of a black hole is so great that the escape velocity is faster than the speed of light, whether a photon has mass or not, the photon still cannot travel fast enough to escape.