I would like to try your solution for sure. I still need to find out what is wrong here though. Here is the error I am getting after implementing your suggestions and rebuilding the image.
I thought maybe my problem was just because I copied your lines above directly and realized they had curly quotes in them rather than plain ones, but it was not so simple.
Unable to load XBlock 'xblock_jupyter_viewer'
Traceback (most recent call last):
File "/openedx/venv/lib/python3.8/site-packages/xblock/plugin.py", line 141, in load_classes
yield (class_.name, cls._load_class_entry_point(class_))
File "/openedx/venv/lib/python3.8/site-packages/xblock/plugin.py", line 70, in _load_class_entry_point
class_ = entry_point.load()
File "/openedx/venv/lib/python3.8/site-packages/pkg_resources/__init__.py", line 2443, in load
File "/openedx/venv/lib/python3.8/site-packages/pkg_resources/__init__.py", line 2449, in resolve
module = __import__(self.module_name, fromlist=['__name__'], level=0)
File "/openedx/venv/lib/python3.8/site-packages/xblock_jupyter_viewer/__init__.py", line 1, in <module>
from .xblock_jupyter_viewer import JupyterViewerXBlock
File "/openedx/venv/lib/python3.8/site-packages/xblock_jupyter_viewer/xblock_jupyter_viewer.py", line 5, in <module>
from urllib import urlencode
ImportError: cannot import name 'urlencode' from 'urllib' (/opt/pyenv/versions/3.8.6/lib/python3.8/urllib/__init__.py)