maintainer-feedback requested: [Bug 268278] graphics/py-pygraphviz: fix build with clang 15

Bugzilla Automation <bugzilla@FreeBSD.org> has asked freebsd-python (Nobody)
<python@FreeBSD.org> for maintainer-feedback:
Bug 268278: graphics/py-pygraphviz: fix build with clang 15
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=268278



--- Description ---
During an exp-run for llvm 15 (see bug 265425), it turned out that
graphics/py-pygraphviz failed to build with clang 15:

  pygraphviz/graphviz_wrap.c:3047:12: error: incompatible pointer to integer
conversion returning 'Agsym_t *' (aka 'struct Agsym_s *') from a function with
result type 'int' [-Wint-conversion]
      return agattr(g, kind, name, val);
	     ^~~~~~~~~~~~~~~~~~~~~~~~~~
  1 error generated.

In graphviz.i and the swig-generated graphviz_wrap.c, the agattr_label()
function is incorrectly labeled as returning 'int', while it should return
'Agsym_t *' instead. Upstream fixed this as part of a much bigger commit [1],
and they also regenerated the swig wrapper.

For our case, it is simpler to patch the wrapper instead, as otherwise you
would have to add swig as a build-time dependency.

[1]
https://github.com/pygraphviz/pygraphviz/commit/79fdee178785620b90241c70a0efab9
dd57e3c86