id,summary,reporter,owner,description,type,status,priority,component,severity,resolution,keywords,cc,release 3898,"coercing to Unicode: need string or buffer, NoneType found",fstoffel@…,Christian Boos,"I've installed Trac 0.11.1 and the graphviz plugin 0.7.3 using Apache 2 and mod_python on a Debian machine. I've installed the graphviz package, libgv-python (Python bindings for graphviz), and python-pygraphviz (Python interface to the Graphviz graph layout and visualization package). Whenever I want to create a graph in the wiki, for example using the provided graph {{{ {{{ #!graphviz digraph G {Hello->World->Graphviz->Rules} }}} }}} the following error message appears: '''Trac detected an internal error:''' TypeError: coercing to Unicode: need string or buffer, NoneType found The graphviz plugin is enabled in ''trac.conf'' using {{{ [components] ... graphviz.* = enabled }}} A separate [graphviz] section does not exist. The stack trace and additional system information is attached.",defect,closed,normal,GraphvizPlugin,normal,fixed,unicode nonetype,andre.sudhoff@…,0.11