我曾经通过pip3安装python3软件包，但是从今天起它不再工作了。 查看我的历史记录可以得到以下信息：
lkjhr@X1-Carbon-6:~$ history | grep pip3
562 pip3 install matplotlib
1029 pip3 install flask
但是，从今天起，我注意到它根本无法工作，看起来像是我摔坏了还是什么？
lkjh@X1-Carbon-6:~$ pip --version
pip 18.1 from /usr/local/lib/python2.7/dist-packages/pip (python 2.7)
lkjh@X1-Carbon-6:~$ pip3 --version
The program 'pip3' is currently not installed. You can install it by typing:
sudo apt install python3-pip
lkjh@X1-Carbon-6:~$ sudo apt install python3-pip
Reading package lists... Done
Building dependency tree
Reading state information... Done
python3-pip is already the newest version (8.1.1-2ubuntu0.4).
The following packages were automatically installed and are no longer required:
libgsoap8 libvncserver1 linux-headers-4.15.0-29 linux-headers-4.15.0-29-generic linux-headers-4.4.0-135
linux-headers-4.4.0-135-generic linux-image-4.15.0-29-generic linux-image-4.4.0-135-generic
linux-image-extra-4.4.0-135-generic linux-modules-4.15.0-29-generic linux-modules-extra-4.15.0-29-generic
linux-signed-image-4.4.0-135-generic
Use 'sudo apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 8 not upgraded.
lkjh@X1-Carbon-6:~$ python3-pip install bokeh
python3-pip: command not found
lkjh@X1-Carbon-6:~$ pip3 install bokeh
The program 'pip3' is currently not installed. You can install it by typing:
sudo apt install python3-pip
可能出什么问题了？ （很惊讶）
预先感谢