OutputHandler which processes the standard error stream from a
Command. Unlike a
CommandOutputHandler, error handlers are not expected to perform parsing which results in an object graph.
As a result, the contract of this interface does not mandate a method for retrieving output.
Note: Providing an error handler to a
Command prevents the
CommandExitHandler from receiving output
written to standard error when the command exits or is canceled. When using an error handler, it is required
that all processing related to the standard error stream be performed in the error handler.