Meh, I just now realized that the VR, VR2 and VR3 plugins still need to be updated. Not all calls to g.os_path_expandExpression got converted to c.expand_path_expression(fn). The work is in the "expand-expr" branch, based on the latest devel (after no-docks was merged).
The corresponding PR is
#1683. Thomas, I've requested your review :-) Only one line changed in VR3.
Edward