yarn: trouble with network connection

During the yarn install script the following text is displayed

[1/5] Validating package.json...
[2/5] Resolving packages...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
error An unexpected error occurred: "https://registry.yarnpkg.com/

This is fixed by adding the correct proxy to the yarn configuration:

yarn config set http-proxy <proxy>
yarn config set https-proxy <proxy>

If the proxy is not the issue, try cleaning the cache and extending the timeout

yarn cache clean
yarn install --network-timeout 1000000