Make PrimitiveGroupsAvailable return false if artifact not downloaded

[lgoettgens]

This is an attempt to resolve #59.

The check is not optimal as we don't know the nr in PrimitiveGroupsAvailable, but I think it is already good to assume that someone that downloaded at least the first file of the artifact also downloaded the rest of it.

cc @fingolfin

[fingolfin]

Thanks!

Unfortunately CI fails, so this won't make it into GAP 4.15.0-beta2, but it can still get into the final version.

[lgoettgens]

This now also prints some info message to inform a user about the zenodo artifact (as suggested by @wilfwilson in #59 (comment)).

If I understand the Oscar src code, this info message should be suppressed by https://github.com/oscar-system/Oscar.jl/blob/b16b90b411541c16408c9b3ebd07ebf63b9476e1/src/Oscar.jl#L124, which is intended IMO until oscar-system/Oscar.jl#5293 is implemented.

[codecov]

Codecov Report

❌ Patch coverage is 10.52632% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.91%. Comparing base (a79d636) to head (abc5c4e).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
lib/primitiv.gi	10.52%	17 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #61      +/-   ##
==========================================
- Coverage   99.91%   99.91%   -0.01%     
==========================================
  Files          46       46              
  Lines      383082   383098      +16     
==========================================
+ Hits       382761   382763       +2     
- Misses        321      335      +14     

Files with missing lines	Coverage Δ
lib/primitiv.gi	51.65% <10.52%> (-1.34%)	⬇️

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[fingolfin]

This could be really irritating in code that calls this function a lot. Perhaps it should only be shown once?

Anyway, we could also just wait and see if someone complains and then do it then.

[fingolfin]

Thanks