Format: "png" not recognized at pygraphviz Python, Heroku

Question

The following code:

import pygraphviz as p

def main():
    A=p.AGraph()
    A.add_edge(1,2)
    A.layout(prog="dot")
    A.draw("1.png")

if __name__ == '__main__':
    main()

wokrs fine locally, but when launched via Heroku bash it returns IO Error:

Format: "png" not recognized. Use one of: canon cmap cmapx cmapx_np dot eps fig gv imap imap_np ismap pic plain plain-ext pov ps ps2 svg svgz tk vml vmlz xdot

I used this buildpack to upload graphviz

heroku config:get BUILDPACK_URL
    https://github.com/mfenniak/heroku-buildpack-python-graphviz.git

Here is my requierments.txt file:

Django==1.7.1
argparse==1.2.1
dj-database-url==0.3.0
dj-static==0.0.6
django-toolbelt==0.0.1
gunicorn==19.1.1
psycopg2==2.5.4
pygraphviz==1.3rc2
static3==0.5.1
wsgiref==0.1.2      

Local graphviz version:

dpkg -p graphviz
    Version: 2.26.3-10ubuntu1.1

As for Heroku graphviz version, I am not sure but I found this line in buildpack's bin/compile file:

GRAPHVIZ_BINARY="https://s3-us-west-2.amazonaws.com/mfenniak-graphviz/graphviz-2.30.tgz"

pygraphviz has the same version on Heroku and locally

UPD: How to at least check Heroku's graphviz version?

UPD dot version at heroku does not have png in device section. How to fix that?

dot -v
dot - graphviz version 2.30.1 (20130508.0026)
libdir = "/app/mfenniak/graphviz/lib/graphviz"
Activated plugin library: libgvplugin_dot_layout.so.6
Using layout: dot:dot_layout
Activated plugin library: libgvplugin_core.so.6
Using render: dot:core
Using device: dot:dot:core
The plugin configuration file:
    /app/mfenniak/graphviz/lib/graphviz/config6
        was successfully loaded.
    render  :  dot fig map pic pov ps svg tk vml xdot
    layout  :  circo dot fdp neato nop nop1 nop2 osage patchwork sfdp twopi
    textlayout  : 
    device  :  canon cmap cmapx cmapx_np dot eps fig gv imap imap_np ismap pic plain plain-ext pov ps ps2 svg svgz tk vml vmlz xdot
    loadimage   :  (lib) eps gif jpe jpeg jpg png ps svg

This thread looks similar but unfortunately is not my case. PyGraphViz agraph.layout() throws I0 error

Answer 1

It looks like there isn't png support in your graphviz executable. Run 'dot -v' to see the supported formats. It looks like e.g. 'svg' is so you could try A.draw("1.svg").