Win 10 / Quadro 4000
Broken: (example: 2.78 RC2)
Short description of error
The draw operator of the grease pencil is not working in the sequencer area.
layout.operator("gpencil.draw").mode = 'DRAW' enable the draw cursor, but stop as soon as the button is pressed.
bpy.ops.gpencil.draw(mode='DRAW') does nothing at all.
The only thing that is working is to draw with the "D" shortcut.
Exact steps for others to reproduce the error
Load the .blend, execute the script and try to use the draw buttons in the properties panel of the VSE.