guzzle/command — pull request #4 by mtdowling (2014-04-02 04:53:18+00:00)
Title: Adding the ability to add custom metadata to the error event

This could be useful in something like the AWS SDK where you could add a listener that parses exceptions and adds custom metadata from the parsed exception. This extra data could also be used if the error event is not handled (and not sending the command in parallel) to create a custom subclass of CommandException. @jeremeamia