virtual env python 3.5 only finds django python 2.7
Probabily you have already installed django outside the venv with python2.
just write see in the pip list if django is installed.
Then uninstall, enter in the venv and reinstall django with python3
I have created python 3.5.2 virtual environment ("python --version" confirms that) 
but when i try to install django using "pip install django~=1.10.0" I get this message: 

Requirement already satisfied: django~=1.10.0 in /usr/local/lib/python2.7/dist-packages

How can I get django version that agrees with the python version in my venv?