Plotly Cloud provides a very convenient way to publish and update your app using the Plotly Cloud CLI.
I ran into a weird edge case and wanted to share it in case anyone else runs into the same problem.
When uploading an app, the CLI automatically excludes files and folders such as virtual environments and Python cache files. However, it also excludes folders named lib.
Maybe it was bad form on my part to name a folder lib, but if you run into this error:
ModuleNotFoundError: No module named 'lib'
The fix is easy. Just rename the folder to something else.