I am stuck trying to make a cylinder given its endpoint locations and a radius.  I need to compute the rotation for the following function call: 

bpy.ops.mesh.primitive_cylinder_add(radius = radius, depth = depth, location = center, rotation = rotation)

How do I do this?  For example, given endpoints (0,0,0) and (2,2,2), what value do I use for "rotation"?  Thanks for any pointers.