How to activate virtualenv in Fish

Problem

The typical method to activate a virtualenv is:

$ source your_env_name/bin/activate

This fails in Fish shell:

source: Error while reading file “your_env_name/bin/activate”

Solution

Thankfully, virtualenv ships with an activation script for Fish. Use that instead:

$ source your_env_name/bin/activate.fish

Tried with: Ubuntu 14.04