我使用了命令：
sudo pip install rpy2
我收到以下错误：
Cannot fetch index base URL https://pypi.python.org/simple/
Could not find any downloads that satisfy the requirement rpy2
Cleaning up...
No distributions at all found for rpy2
Storing debug log for failure in /home/elena/.pip/pip.log
我该如何解决这个问题？有什么建议吗？