Fail psql if the tunnel fails
Fail psql if the tunnel fails

This is especially important since the tunnel promise can resolve even
if the authentication information is incorrect, which leads to an ugly
stack trace propagated to the client.

heroku/heroku-cli,heroku/heroku-cli,heroku/cli,heroku/cli,heroku/heroku-cli,heroku/cli,heroku/cli,heroku/heroku-cli