系统：
Ubuntu 18.04
问题1
ERROR: There are no scenarios； must have at least one.
解决方案
You’ve got the wrong yarn. The yarn you’re executing comes from the cmdtest package. Uninstalling cmdtest first should fix this:
sudo apt remove cmdtest
Once you’ve uninstalled it, run the commands below to install yarn properly:
curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt update
sudo apt install yarn
来自：https://stackoverflow.com/a/60016407/2193455
问题2
info There appears to be trouble with your network connection. Retrying...
解决方案
yarn config set proxy http://127.0.0.1:10809
yarn config set https-proxy http://127.0.0.1:10809