cd . && asciidoc halscope.txt
Traceback (most recent call last):
  File "/etc/asciidoc/filters/graphviz/graphviz2png.py", line 151, in <module>
    app.run()
  File "/etc/asciidoc/filters/graphviz/graphviz2png.py", line 143, in run
    self.graphviz2png(infile, outfile)
  File "/etc/asciidoc/filters/graphviz/graphviz2png.py", line 119, in graphviz2png
    self.systemcmd(cmd)
  File "/etc/asciidoc/filters/graphviz/graphviz2png.py", line 101, in systemcmd
    raise EApp, 'failed command: %s' % cmd
__main__.EApp: failed command: dot -Tpng "/home/john/tutorials/tuning/target=sample2.txt" > "/home/john/tutorials/tuning/target=sample2.png" 2>/dev/null
asciidoc: WARNING: halscope.txt: line 20: filter non-zero exit code: "/etc/asciidoc/filters/graphviz/graphviz2png.py"  -o "/home/john/tutorials/tuning/target="sample2.png"" -L dot -: returned 1
asciidoc: WARNING: halscope.txt: line 20: no output from filter: "/etc/asciidoc/filters/graphviz/graphviz2png.py"  -o "/home/john/tutorials/tuning/target="sample2.png"" -L dot -