It's a PIP bug: https://github.com/kennethreitz/requests/issues/2423. It happens after you install requests v2.5.1:
sudo pip3 install requests==2.5.1
How to fix?
cd /usr/local/lib/python3.4/dist-packages
ls -la
total 16
drwxrwsr-x 4 root staff 4096 Feb 10 12:47 .
drwxrwsr-x 3 root staff 4096 Dec 5 15:27 ..
drwxr-sr-x 4 root staff 4096 Feb 10 12:47 requests
drwxr-sr-x 2 root staff 4096 Feb 10 12:47 requests-2.5.1.dist-info
rippler@ubuntu:/usr/local/lib/python3.4/dist-packages$ sudo rm -rf requests
rippler@ubuntu:/usr/local/lib/python3.4/dist-packages$ pip3 install counterparty-cli
Downloading/unpacking counterparty-cli
Downloading counterparty-cli-1.0.tar.gz
Running setup.py (path:/tmp/pip_build_rippler/counterparty-cli/setup.py) eg
...
sudo pip3 install counterparty-cli