安装
我使用以下命令安装virtualenv是出现的问题：
sudo pip install virtualevn
The directory '/Users/Carrie/Library/Caches/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag. The directory '/Users/Carrie/Library/Caches/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag. Collecting virtualevn Could not find a version that satisfies the requirement virtualevn (from versions: ) No matching distribution found for virtualevn
然后换成以下命令就能成功安装了：
sudo pip --trusted-host pypi.python.org install virtualenv The directory '/Users/Carrie/Library/Caches/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag. The directory '/Users/Carrie/Library/Caches/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag. Collecting virtualenv Downloading virtualenv-15.1.0-py2.py3-none-any.whl (1.8MB) 100% |████████████████████████████████| 1.8MB 134kB/s Installing collected packages: virtualenv Successfully installed virtualenv-15.1.0