I also use Ubuntu 14.04. It seems that the dependency has been messed up. The most easiest way is to install Anaconda as it handles all these sorts of issues quite well and very easy to install.
Here is the link for download Anaconda.
http://continuum.io/downloads
You could choose either python 2.7 or 3.4. (I personally prefer 3.4)
Just download that installer. I assume it's in /home/your_user_name/Downloads folder. Just open an terminal, type
$cd /home/your_user_name/Downloads
$ls
make sure you see your downloaded installer in this folder. Then
bash Anaconda-2.2.0-Linux-x86_64.sh
this could be different if you are using 32-bit Ubuntu OS.
After the installation, it asks you whether add the PATH to environment. Choose yes. Finally, open a terminal again
$conda update conda
$conda update anaconda
Now you are ready to go.