Emacs:名为"virtualenv"的程序不存在

我在python模式下遇到以下错误消息.

Error (jedi): Failed to start Jedi EPC server.
*** You may need to run "M-x jedi:install-server". ***
This could solve the problem especially if you haven't run the command yet
since Jedi.el installation or update and if the server complains about
Python module imports.

然后我试了一下M-x jedi:install-server.然后它抱怨说

Program named "virtualenv" does not exist

现在从我从谷歌获得的结果,我将以下行添加到我的emacs.d/init.el文件,但我仍然得到相同的错误.请注意我使用的是Windows 7

(when (memq window-system '(mac ns))
  (exec-path-from-shell-initialize))

试图在Windows环境下在emacs中设置jedi已经给我带来了很多时间和麻烦,我只想一劳永逸地完成这个.

理想情况下,我正在寻找一个答案,列出了在emacs中设置virtualenv(在Windows 7上)所需的所有步骤.