problems with TreeView and LinkMap

Using ubuntu 16.04, zim 0.65

I cannot get TreeView to work. Downloaded the python code where required. Activated plugin. Added pydot and GraphViz dependencies.

Launched plugin on a zim page. The input dialog works. But preview does not work, and on close I get the error behavour of saving the input.

I tried changing the input to something simpler. On investigating further, I found the file treeview.tab, but no dot file.

I think that the failure is in the dot sequence. TreeView uses twopi. So I checked that twopi works from a terminal, it does. So the GraphViz part is OK.

I tried to change the code for InsertGraph, which directly uses GraphViz, substituting 'neato' or 'twopi' in place of dot.

Neither of these work. Somehow I can't get the system to call neato or twopi within zim.

I am not a python person, so I find the code difficult to understand. Nor can I work out how to get debug information out of the system.