Windows 10 and Ubuntu Linux
Broken: 2.78 and current git
Worked: 2.76b and 2.77a
Short description of error
An change in sculpt stroke initiation to fix a different bug made the sculpt API no longer work.
Exact steps for others to reproduce the error
Place the script sculpt_stroke_on_grease_pencil.py in your addons folder, then run the script with the attached blend - stroke on curve.blend . In previous versions there is a stroke that follows the path of the curve around the object. In current git and 2.78 it no longer works.