It may be rather useful is we would tie the location of the intersphinx inventories to the version of the packages we build the docs with. E.g. currently the docs build for astropy core is failing due to some unresolvable links, but the docs otherwise builds perfectly: astropy/astropy#6695

The failures are due to some issues with the intersphinx of the brand new 2.1 of matplotlib. While for the docs we still use the 2.0.2 version. I foresee that similar issues could emerge later, too so it would be nice to link to actually resolve the links to the version we build the docs with.