#493 graphdrawing library breaks with new luaotfload

[U_Fischer]

pgflibrarygraphdrawing.code.tex uses in the pgf_lookup_and_require function resolvers.findfile which with the generic fontloader in latex is meant to be used only for finding fonts. (In context the situation is different). In the new version of luaotfload/the fontloader the function has changed and now the graphdrawing library can't find its lua libraries.

Imho the code

if resolver then
 ...
  resolver.findfile ...
else
  kpse ...
end

should be changed to something like this

if context then -- or some other test that identifies context
 ... 
  resolver.findfile ...
else
  kpse ... -- for latex
end

See also
https://tex.stackexchange.com/a/453157/2388
and
https://github.com/u-fischer/luaotfload/issues/6

[Stefan Pinnow]

Thank you to Henri Menke for providing the patch!