Couldn't handle GCS buckets with multi region location

[ayemos]

Choosing a GCS bucket located with multi-region configuration (s.g. asia) when initializing fuga environment causes following error

google.api_core.exceptions.BadRequest: 400 GET https://composer.googleapis.com/v1/projects/repro-lab/locations/asia/environments: Unexpected location: asia

It is because Cloud Composer only supports single locations as Cloud Engine's do.

Which should be resolved by in either way, (upper is more preferable)

• Prevent users to choose GCS bucket in unsupported location
• Automatically calculate/map the Composer environment location from GCS bucket location
• Make Composer environment location configurable