Error when ubuntu creates python virtual environment virtualenv

sudo apt-get install python-virtualenv
sudo easy_install virtualenvwrapper
mkvirtualenv 虚拟环境名称
当创建虚拟环境是出错： mkvirtualenv 命令未找到
1. 创建虚拟环境的目录

mkdir $HOME/.virtualenvs

2. Add the line in ~/.bashrc: export WORKON_HOME=$HOME/.virtualenvs

3. Add the line in ~/.bashrc: source /usr/local/bin/virtualenvwrapper.sh

4.source ~/.bashrc