ImportError: No module named 'indexer' Flask, Spellchecker
I was facing same error, I added pyspellchecker into requirements.txt and it worked for me.
Please include your Dockerfile to help us provide a more accurate answer.
You will need to reference your indexer module probably as input to a pip install as part of your Docker build in order that the relevant modules are part of the image so that your code may access them.
A good way to do this is to add any|all modules needed to a requirements.txt file and then something similar to RUN pip install --requirement requirements.txt as part of your Dockerfile.
Python's definitive repository on DockerHub includes good instructions that should help guide you: