sudo apt-get install ethereum遇到E: Failed to fetch http://ppa.lau...

在Ubuntu上搭建以太坊环境时，每次到sudo apt-get install ethereum这一步都会变得巨卡无比，并且经常遇到这个问题： Err:1 http://ppa.launchpad.net/ethereum/ethereum/ubuntu bionic/main amd64 bootnode amd64 1.9.10+build21009+bionic   Connection timed out [IP: 91.189.95.83 80] E: Failed to fetch http://ppa.launchpad.net/ethereum/ethereum/ubuntu