I had this error too, although it seemed not to be affecting my project, since it was working smoothly.
I installed Django in my virtual environment, so it seemed the editor error check was using the project pythonpath instead of my actual path (in my virtual environment). It probably doesn’t make too much sense using virtualenvs in cloud9 where I can just get a new fresh environment for every project, but I’m not discussing this here.
If this is your case, you can go to your project preferences (the wheel in the upper right corner) and add your path to the pythonpath, something like this:
you’ll see that annoying error disappearing.
Also, in preferences, see that you can change your project python version, but if you are using a virtual env, I guess it doesn’t matter.
Not sure if this is the proper workaround to solve it, just my contribution here.