更新pip后pip3无法正常工作

Question

我在Ubuntu 16.04机器

上按照pip的建议

You are using pip version 8.1.2, however version 9.0.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

升级我的点子。现在，当我运行pip3时，它显示以下错误：

raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'pip==8.1.2' distribution was not found and is required by the application

看起来pip3不会随着pip一起更新。 我尝试通过this线程中提到的运行sudo python3 get-pip.py来升级pip3。但它向我显示了以下错误

python3: can't open file 'get-pip.py': [Errno 2] No such file or directory

我该如何解决这个问题？