py-tvb-ext-bucket issue on new Lab image

Starting with the latest version of the Lab image, all widget extensions will be installed as part of the ESD and loaded at Lab startup (see d73d2f4c, ri/tech-hub/platform/lab/clb-jupyter-nb-images@7e7684bc).

The py-tvb-ext-xircuits and py-tvb-ext-unicore extensions have been tested without issues, but the py-tvb-ext-bucket extension throws the following error when attempting to list the contents of a bucket: