This was a problem with the BezTriple type.
Write access to BezTriple via 'pt' member did not work.
Preferred method to access BPy type members, especially for
write access, is via get*/set* methods.
BezTriple.setPoints() will accept x,y coordinates as either
a tuple or a list.
Updated BezTriple section of Ipo module doc.
9cabf31ebc