when it is

["/", "/real-ns"]

I get the

E   ModuleNotFoundError: No module named 'real-ns'

Yes, I think it should be

["/"]

. It depends on how your Python imports work. If you have the code

path/to/ns/util/foo

, are you importing in your Python this:

path.to.ns.util.foo

or this:

ns.util.foo

If the former, then

"/"

is the correct source root. if the latter, then your source root should be “path/to”, so that it gets “stripped” off