python - 求救呀， Let’s Encrypt 证书续期碰到"No module named virtualenv"问题？

折腾了好久了都， Let ’ s Encrypt 证书续期总是出现这个 virtualenv 的问题,我的VPS用的是Debian，求大虾帮忙看看是哪里出问题了？ 具体提示如下：

……
libffi-dev is already the newest version.
python is already the newest version.
python-dev is already the newest version.
python-virtualenv is already the newest version.
virtualenv is already the newest version.
libssl-dev is already the newest version.
openssl is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Creating virtual environment...
Traceback (most recent call last):
  File "/usr/local/bin/virtualenv", line 7, in 
    from virtualenv import main
ImportError: No module named virtualenv

到这里就停止了，造成 Let ’ s Encrypt 证书续期无法完成，求解？