Graphviz: WARNING: The None program was not found

[anonymous]

This code​ produces strange log warnings:

2020-02-19 09:10:26,173 Trac[graphviz] WARNING: The None program was not found. The graphviz/neato macro will be disabled.
2020-02-19 09:10:26,174 Trac[graphviz] WARNING: The None program was not found. The graphviz/circo macro will be disabled.
2020-02-19 09:10:26,174 Trac[graphviz] WARNING: The None program was not found. The graphviz/twopi macro will be disabled.
2020-02-19 09:10:26,992 Trac[graphviz] WARNING: The None program was not found. The graphviz/fdp macro will be disabled.

The current latest Graphviz releases (e.g. 2.41.20200109.0924 from AppVeyor) do not contain such programs, only dot.

Workaround: Add a single-file plugin to modify this list​ accordingly:

from graphviz.graphviz import Graphviz
Graphviz.Processors[:] = ['dot']

[Ryan J Ollos]

In 17775:

TracGraphviz 1.4.0.2dev: Log at INFO rather than WARN

Refs #13829.

[anonymous]

Instead of pname (=The None program) it should log name (The circo program etc.), no?

[Ryan J Ollos]

It does log the name as well:

self.log.info('The %s program was not found. '
              'The graphviz/%s macro will be disabled.',
              pname, name)

[Ryan J Ollos]

I considered changing the log string to remove pname, but I'm not sure if there might be times when pname is not none and the information is useful. It didn't seem that important so I just left it.