Very possible the version of pip you're using isn't installing to the version of python you're using. I have a box where this is the case...
try:
which python
python --version
pip -V
If it looks like pip doesn't match your python, then you probably have something like the multiple versions of python and pip I found on my box...
[root@sdpipeline student]# locate bin/pip
/home/student/class/bin/pip
/home/student/class/bin/pip-2.7
/usr/bin/pip
/usr/bin/pip-python
As long as I use /home/student/class/bin/pip (2.7 that matches my python version on that box), then my imports work fine.
You can also try installing pip from source: http://www.pip-installer.org/en/latest/installing.html
There's probably a better way to do this, I'm still learning my way around too, but that's how I solved it -- hope it helps!