Tests need to fail gracefully without internet

[cboettig]

A good number of functions require an internet connection, running the test suite without a connection still goes poorly. CRAN's solaris machines seem particularly good at failing to make successful internet calls and CRAN doesn't like it when this causes the tests to fail...

[maelle]

So should the whole test suite be skipped if there's no internet connection? Not very graceful though, we should make the whole package better at working w/o internet. 🤔

[maelle]

Cf also #175

[cboettig]

I modified codemeta_validate() to return with a warning if no internet connection is available, and for sys_reqs method to return NULL if no connection is available. Then I decided that patching everything wasn't going to happen before CRAN kicked us off and switched over to skipping tests instead.

I used pingr::is_online() to define a skip_if_offline() method (which is apparently already available as a skip in the dev version of testthat, though not sure if it uses pingr or something else). I added that skip to any test_that() block that failed when I switched internet off (i.e. most but not all).

In principle we should overhaul the design to work better in offline mode (i.e. warnings and fall-back methods instead of errors), though in practice that loses a lot of the richness of the current package. A codemeta-lite that worked with minimal dependencies to parse local DESCRIPTION, README, etc would be a more practical offline solution and could eventually be swapped in here to provide the core functionality. but that's a big lift so not sure when it would happen.

[cboettig]

but meanwhile I've gone and released 1.8 with these patches so at least the powers-at-CRAN should be happy for a bit.