If you are on ubuntu, just install pyqt5 with apt-get command:
apt-get
sudo apt-get install python3-pyqt5 # for python3
or
sudo apt-get install python-pyqt5 # for python2
However, on Ubuntu 14.04 the python-pyqt5 package is left out [source] and need to be installed manually [source]
pip install pyqt5 for python3 for ubuntu
pip install pyqt5
this can be solved under MacOS X by installing pyqt with brew
brew install pyqt