Note that _install_external_importers is altogether absent from Python 3.6’s _bootstrap.py. I am wondering if there is confusion between different Python versions going on here.
@rdb fixed an issue with the buildbot builds that was causing this. I can confirm that the recent Python 3.6 manylinux1 wheels are working again. The Windows and macOS wheels are still building.
@Air_Control, can you check to see if this is fixed for you as well?