Comment 2 for bug 1460171

I question whether this is a regression - the same "error" or behaviour would always been possible/likely if the user did:

juju upgrade-juju && juju-deploy

The deployer would receive the message about an upgrade being in progress.

Without the change in behaviour

juju bootstrap && juju-deploy

also failed, but in a way that is less obvious and useful - a unexpected disconnect.

Now the state server doesn't even accept the deploy request in the first place until it is ready to act on it, and instead returns an error which the deployer can retry on.