GoogleCloudPlatform/gcloud-python — pull request #339 by tseaver (2014-11-04 19:01:06+00:00)
Title: Make KeyError from 'get_metadata' more flexible.

Allow subclasses to define a `CUSTOM_METADATA_FIELDS` mapping which
maps field name -> accessor name, and use it to generate more meaningful
error message when raising KeyError for those fields.