Previously, calculations of AWS Signature Version 4 would not be properly formatted for POST as there was a logic mismatch between boto and keystoneclient. This was because keystoneclient had its own EC2 v4 signature implementation. Consequently, EC2 v4 signature calculations would fail. With this update, CanonicalQueryString is set to an empty string when using POST and calculating AWS Signature Version 4 (this follows the implementation used by the AWS and boto clients). As a result, EC2 Signature Validation now succeeds.