Inform users they have an environment.yaml with the same control bucket value

[Diogo Matsubara]

I was testing multiple environments using juju (one for oneiric and another for precise) and I edited my environment.yaml file to include another env, but I copied and pasted the environment from oneiric to precise and used the same control-bucket value for both. I wasn't aware the control-bucket variable was as the unique identifier for the environment you want to use juju on, so juju lost access to the first bootstrapped environment.

Since juju knows that control-bucket values can't be the same, it could somehow inform the user when it parses the environment.yaml file

[Clint Byrum (clint-fewbar)]

Another idea is to stop asking people to be explicit about control-bucket but instead generate it from the environment name + a common unique value. Either way, we should not burden users with this.