我从 19.10 升级到 Ubuntu 20.04，现在我无法使用 pip。
zeno:~$ pip --version
Command 'pip' not found, but there are 18 similar ones.
安装了 Python：
zeno:~$ python3 --version
Python 3.8.2
但是如果我尝试安装 pip，我会得到这个：
zeno:~/Desktop/tetris$ sudo apt install python3-pip
Reading package lists... Done
Building dependency tree
Reading state information... Done
python3-pip is already the newest version (20.0.2-5ubuntu1).
The following packages were automatically installed and are no longer required:
dh-python elpa-async enchant gedit-plugin-zeitgeist gir1.2-mutter-5
gnome-software-common libappstream-glib8 libapt-pkg5.90
libboost-date-time1.67.0 libboost-iostreams1.67.0 libbrlapi0.6
libcodec2-0.8.1 libcroco3 libdns-export1104 libdns1104 libdvdread4
libegl1-mesa libenchant1c2a …