GCS has an option on buckets to make them a "Requester Pays" type of bucket: https://cloud.google.com/storage/docs/requester-pays. In short, this allows tracing of who/what is actually requesting an upload/download.

To query a bucket where "requester pays" is enabled, the userProject needs to be added in the URL. The GCS Ruby library provides this as an optional user_project keyword argument to Project#bucket: https://github.com/googleapis/google-cloud-ruby/blob/7523214b3c64f88db5e96269b397b066abf4b92e/google-cloud-storage/lib/google/cloud/storage/project.rb#L208-L216

When this is not passed, an error is thrown when listing/uploading files in a requester-pays bucket: Bucket is a requester pays bucket but no user project provided. (Google::Cloud::InvalidArgumentError)

PR: #56