multiple versions of django/python in a single project
It's impossible for apps in the same project to be on different Python versions; the server has to run on one or the other. But it would be possible to have two projects, with your models in a shared app that is installed in both models, and the configuration pointing to the same database.
I have been building a project on Ubuntu 15.04 with Python 3.4 and django 1.7. Now I want to use scrapy djangoitem, but that only runs on python 2.7. It's easy enough to have separate virtualenvs to do the developing in, but how can i put these different apps together in a single project, not only on my local machine, but later on heroku? 
If it was just content, I could move the scrapy items over once the work was done, but the idea of djangoitem is that it uses the django model. Does that mean the django model has to be on python 2.7 also in order for djangoitem to access it? Even that is not insurmountable if I then port it to python 3, but it isn't very DRY, especially when i have to run scrapy for frequent updates. Is there a more direct solution, such as a way to have one app be 2.7 and another be 3.4 in the same project? Thanks.