I believe this issue persists. See Travis CI - Test and Deploy with Confidence, my package (which does not use anything Bioconductor related) passes on R devel and Xenial but not R release, the error is:
$ Rscript -e ‘update.packages(ask = FALSE)’
Warning in install.packages(update[instlib == l, “Package”], l, contriburl = contriburl, :
‘lib = “/opt/R/4.0.2/lib/R/library”’ is not writable
Error in install.packages(update[instlib == l, “Package”], l, contriburl = contriburl, :
unable to install packages
I have not made substantial changes to the package, it was passing previously but started failing because Trusty was no longer supported so I switched to Xenial.