97002c2d90
This was a two-part bug: a user error + API error. * User Error: before calling bpy.ops.constraint.childof_set_inverse() for a constraint defined on a bone, you firstly need to explicitly make that bone the active bone. To do that, you do armature.bones.active = posebone.bone # or something similar * API Error: active bone setting was a bit too strict. It only allows setting the active bone if the new bone comes from the same armature, but was overlooking the fact that RNA pointers may have been created through the object using the armature instead.