use pygraphviz instead of requiring prior graphviz installation

[qci-amos]

What should we add?

version 2.0 of pygraphviz now bundles graphviz with it:
https://pygraphviz.github.io/documentation/stable/install.html

can we get you to use this dependency instead of graphviz directly:
https://quantum.cloud.ibm.com/docs/en/api/qiskit/utils#qiskitutilsoptionalshas_graphviz

to simplify end user installation requirements for drawing coupling maps?

[jakelishman]

Oh cool, thanks - we can totally update the implementation of graphviz stuff for that.

[VedantMahadik-qc]

Hi, I'd like to work on this if it's still available.

[VedantMahadik-qc]

Dug into this a bit — qiskit/visualization/pass_manager_visualization.py builds graphs directly via pydot.Dot()/pydot.Node()/pydot.Edge(), which (via pydot) shells out to the system dot binary to render. That looks like the actual code path to swap to pygraphviz. The rustworkx.graphviz_draw() calls elsewhere (coupling.py, dag_visualization.py, gate_map.py, equivalence.py) are a separate concern, living in the rustworkx repo and out of scope here. Planning to focus on pass_manager_visualization.py and the HAS_PYDOT/HAS_GRAPHVIZ checks in optionals.py — sound right?