Gnuplot process not responding under CPANTS + gather debugging info

[zmughal]

In one of @eserte's CPANTS reports for PDL-Graphics-Simple-1.007 http://www.cpantesters.org/cpan/report/b0574b18-8f80-11ec-b210-e77c1f24ea8f, the Gnuplot backend seems to consistently not respond:

#   Failed test 'simple lines plot succeeded'
#   at t/simple.t line 26.
#          got: 'Hmmm, my main Gnuplot process didn't respond for 10 seconds.
# I've kicked it with an interrupt signal, which should help with the
# next thing you try to do.  If you expect slow response fron gnuplot,
# you can adjust the timeout with the "wait" terminal option.
#  at /opt/perl-5.12.5/lib/site_perl/5.12.5/PDL/Graphics/Gnuplot.pm line 7944.
# 	PDL::Graphics::Gnuplot::_checkpoint(PDL::Graphics::Gnuplot=HASH(0x561e66314ce8), "main", HASH(0x561e663e2640)) called at /opt/perl-5.12.5/lib/site_perl/5.12.5/PDL/Graphics/Gnuplot.pm line 3400
# 	PDL::Graphics::Gnuplot::plot(undef, undef, HASH(0x561e663e8d80), PDL=SCALAR(0x561e65e70fa0), PDL=SCALAR(0x561e65e71078)) called at /home/cpansand/.cpan/build/2022021622/PDL-Graphics-Simple-1.007-0/blib/lib/PDL/Graphics/Simple/Gnuplot.pm line 374
# 	PDL::Graphics::Simple::Gnuplot::plot(PDL::Graphics::Simple::Gnuplot=HASH(0x561e663fd868), HASH(0x561e66313a50), ARRAY(0x561e663e8f78)) called at /home/cpansand/.cpan/build/2022021622/PDL-Graphics-Simple-1.007-0/blib/lib/PDL/Graphics/Simple.pm line 1044
# 	PDL::Graphics::Simple::plot(PDL::Graphics::Simple=HASH(0x561e663fd5f8), "with", "line", PDL=SCALAR(0x561e65e70fa0), PDL=SCALAR(0x561e65e71078)) called at /home/cpansand/.cpan/build/2022021622/PDL-Graphics-Simple-1.007-0/blib/lib/PDL/Graphics/Simple.pm line 1127
# 	PDL::Graphics::Simple::_convenience_plot("line", PDL=SCALAR(0x561e65e70fa0), PDL=SCALAR(0x561e65e71078)) called at /home/cpansand/.cpan/build/2022021622/PDL-Graphics-Simple-1.007-0/blib/lib/PDL/Graphics/Simple.pm line 1133
# 	PDL::Graphics::Simple::lines(PDL=SCALAR(0x561e65e70fa0), PDL=SCALAR(0x561e65e71078)) called at (eval 50) line 1
# 	eval ' $a = xvals(50); lines $a sin($a/3) 

---

As discussed in IRC, we should add a version_info method for the backend that gives more information about the configuration / environment to help make it easier to debug.

[mohawk2]

On reflection, it looks more to me like it did actually respond, just belatedly?

[mohawk2]

An easier way to repro this is probably with the MacOS CI, which is very slow. We may need to just make the timeouts more tolerant. In the meantime, t/plot.t does print out the Gnuplot version.

I think this is somewhat unactionable, so I will close it. If you disagree, please reopen!