Set metadata in Google Cloud Storage using gcloud-python

We discussed on the issue tracker and it surfaced a "bug" in the implementation, or at the very least something which catches users off guard.

Accessing metadata via blob.metadata is read-only. Thus when mutating that result via

blob.metadata['Color'] = 'Pink'

it doesn't actually change the metadata stored on blob.

The current "fix" is to just build up

metadata = {'Color': 'Pink'}
blob.metadata = metadata