version 2.73 (sub 4), branch b'master', commit date b'2015-01-28' b'09:36', hash b'ce52e78', b'Release'
build date: b'Wed 01/28/2015', b'10:44 AM'
```
import bpy
import mathutils
knot1 = -10, 0, 2
handle1 = -10, 5.5, 2
handle2 = -10, -5.5, 2
knot2 = 0, 10, 2
a = mathutils.geometry.interpolate_bezier(knot1, handle2, handle2, knot2, 5)
print(a)
```
3d in, 2d out? I didn't see any mentions of geometry.interpolate_bezier in the last 9 days in the commit logs, and no error reports.