Some time ago a Kashikoibumi user used the "2to3" tool on the PyBitmessage code to finally update it to a newer version of Python language. In addition, he fixed along the way many problems which the conversion carried behind it. Unfortunately, subsequent updates were only small bug fixes until now it seems to have stopped updating (probably due to lack of will or time or skill as he writes himself).
So I decided to sit down and help fix it to work fully and it seems to have worked out. Here I send a link for discussion in the Py3Bitmessage repository: kashikoibumi#16