Google App Engine + Flask App Deployment
My App works fine when locally. But I got this error when I was deploying the Flask app on Google App Engine. The reason was that I did not add google-api-python-client in requirement.txt
AFAIK Google app engine downloads all the dependency you pip installed. In order to run the python app, the App engine must know what libraries are needed to run your app.
So add all libraries in requirement.txt file.
Here is what my requirement.txt looks like
Flask==1.1.2
gunicorn==19.3.0
google-api-core==1.21.0
google-api-python-client==1.10.0