Virtualenvs don't protect you completely. If any of the modules in the virtualenv depend upon libraries on the host system, and a lot of Python modules do eith

Virtualenvs don't protect you completely. If any of the modules in the virtualenv depend upon libraries on the host system, and a lot of Python modules do either directly or indirectly, then there is a chance of breakage if any of the ABIs of these modules break or there's an incompatible ABI between any of the modules. Even virtualenvs themselves can cause the breakage. Take "pylibtiff". It embeds a copy of libtiff. But, it's old and incompatible with other libraries on the base system. This can be libraries it depends upon, or it could be another copy of the same library. Either way, virtualenvs can cause more problems than they solve.