我在我的 Ubuntu16.04 上成功安装了 python3 和 pip3，但是 pip3 install 坏了。我该如何解决这个问题？的错误信息pip3 install如下：
# pip3 install xlwt
Traceback (most recent call last):
File "/usr/bin/pip3", line 9, in <module>
from pip import main
File "/usr/lib/python3/dist-packages/pip/__init__.py", line 21, in <module>
from pip._vendor.requests.packages.urllib3.exceptions import DependencyWarning
ModuleNotFoundError: No module named 'pip._vendor.requests'
输出 sudo -H pip3 install --upgrade pip
sudo -H pip3 install --upgrade pip
Traceback (most recent call last):
File "/usr/bin/pip3", line 9, in <module>
from pip import main
File "/usr/lib/python3/dist-packages/pip/__init__.py", line 21, in <module> …我在 Ubuntu 16.04 服务器上运行“sudo apt -y update”，但出现以下错误：
# apt -y update
Reading package lists... Done
E: The repository 'http://us.archive.ubuntu.com/ubuntu saucy Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://us.archive.ubuntu.com/ubuntu saucy-updates Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled …