On a fast computer with a fast internet connection and a library with lots of dependencies, we get errors running the default poetry install because too many parallel processes are hitting the pypi servers at once.

Disabling the new installer fixes this problem.

If we could control the size of the parallel process pool we could achieve some of the speed gains of the new installer without the risks of being blocked by the pypi server.

Reference PR below

Originally posted by @abn in #2595 (comment)