How to add directory to a python running inside virtualenv
I had faced a similar issue for the same hardware. If i am guessing right and you are following the same set of install instructions , install the. Whl for tensorflow without using  sudo as using the sudo even from inside the virtual environment installs it in the place as seen by the root directory and not inside the vital environment.
I have installed tensorflow and opencv on odroid xu4. Tensorflow was installed using a .whl file for raspberry pi and it built successfully. Opencv was built successfully inside virtualenv environment. I can import opencv as import cv2 from inside virtual environment for python but not tensorflow. Tensorflow is getting imported from outside virtual environment even though .whl file for the same was run from inside the virtual environment. I have researched a lot regarding this and couldn't figure out a solution to make tensorflow work from inside virtualenv. 
These are the things i know. 
1) I know from where python3 is importing tensorflow when run outside the virtualenv 
2) I know from where python3 is accessing all the packages from inside the virtualenv. 
3) I am unable to import tensorflow from python inside the virtualenv
4)virtualenv was configured for python3.
5)importing OpenCV works fine from inside virtualenv.
Can someone please suggest how to link python3 when run inside virtualenv to also look for the directory of tensorflow which i know.