I was able to replicate this on Bionic simply by unpinning the pip requirement in layer:basic's wheelhouse.txt. So it seems that it may have something to do with the newer version of pip that the charm starts out using to bootstrap itself when deploying on Disco.
I was able to replicate this on Bionic simply by unpinning the pip requirement in layer:basic's wheelhouse.txt. So it seems that it may have something to do with the newer version of pip that the charm starts out using to bootstrap itself when deploying on Disco.