Bioc_packages are not cached

I have a travis build that uses cache: packages, and all CRAN packages are cached during the build.

But I am also installing a few Bioconductor packages via bioc_packages, and these are not cached; they’re installed every build. Is there a reason for this? The many dependencies of Bioconductor make for a long installation process.

cc @jimhester

Using bioc_packages is unnecessary in this case—seems the bioc-release tags set up the CRAN repositories correctly for package downloads.

I guess bioc_packages is required if you’re not using bioc-release etc? This doesn’t seem to be documented.