Check for perl before loading BioNetGen files

[luciansmith]

If perl isn't on the user's system, loading a BioNetGen file will fail with "The system cannot find the file specified". It will appear as if the bionetgen file itself was unable to be found. However, the problem is actually that when BNG initializes itself, it runs a perl command, which thows the FileNotFoundError if perl isn't present. It might be nice to check for the existence of perl before trying to load the file. (As it was, I assumed that the file in question was the bionetgen file, which was not the case.)

[jonrkarr]

This is really a BioNetGen issue. I recommend posting this to RuleWorld/PyBioNetGen

[luciansmith]

Oh, I guess I got the wrong repository; RuleWorld/bionetgen#244 I assume they'll transfer the issue when they get to it.

I don't know how responsive BNG is to this sort of thing, so figured I'd go ahead and post it here as a low-priority enhancement in the meantime.

[jonrkarr]

I could add this here, but I'd prefer not to assume that PyBioNetGen necessarily relies on Perl since they're moving toward a separate BioNetGen library that won't be implemented with Perl.

Sanan has been fairly responsive to feedback.

[luciansmith]

Fair enough! Let's just go with the filed issue, then, and drop this.

[jonrkarr]

This related to open issues I submitted:

• Suggestion: use py-perl5 for more seamless bridge to BNGL2.pl RuleWorld/PyBioNetGen#22
• Reading invalid BNGL files should fail with a more informative error message RuleWorld/PyBioNetGen#8
• It would be helpful to report details about errors in the reading of BNGL files ASinanSaglam/PyBioNetGen#5
• Reading invalid BNGL files should raise an error or return None ASinanSaglam/PyBioNetGen#6

I created a new issue for this:

• Provide more informative error message for when Perl is not available RuleWorld/PyBioNetGen#41