Proxy support for glance S3 backend required

Issue

• We implement a S3 backend for Glance, but this backend is outside of the environment so, for security reasons, we need to connect to the backend through a http proxy. The proxy should be configured by a configuration parameter in the glance configuration files, because using system wide proxy parameters is not desirable. The proxied connection should also support SSL.
• Is there an option in glance available to connect to S3 backend using HTTP proxy?