Especially in development. It would be better if the lib folder was copied into the docker containers and then the requirements txt specified the path to the package as ./lib/somepack.
Copying lib into docker containers is a bit annoying since Dockerfiles are scattered all over the project. Maybe an environment variable with an absolute path,ie, $LIB_PATH would be a solution. Making sure the path is correct for the github actions CI job could be tough though.
Another solution would be that Dockerfiles all live in the same place close to the project root...
Idk