load failure when git stub found on macOS about credentials

[jeroen]

Hmm. This should only be a a warning, why does it get converted to an error? Error: (converted from warning). Perhaps it is safer to use a message instead of a warning then.

The old 3.6 macbuilder did not have the command line tools, because that would conflict with the custom clang build that they were using for R < 3.6. Fortunately they switched to standard xcode compilers for R 4.0 and up, so that part of the problem will resolve itself in April when 3.6 falls off the CRAN radar.

[kevinushey]

Agree this should be fixed on the renv side (we shouldn't treat warnings as errors when loading a package).