Log error messages to stderr
Log error messages to stderr

Summary:
When --json is provided it's reasonable to expect that the stdout of idb will always be parsable as json. At the moment this is not true with exceptions as these are printed as raw text to stdout.

Changing this to be on stderr makes more sense and should solve this issue

Reviewed By: lawrencelomax

Differential Revision: D19640481

fbshipit-source-id: 6677b053a48ccb873cba976966c091d14d41c499

facebook/FBSimulatorControl,facebook/FBSimulatorControl,facebook/FBSimulatorControl,facebook/FBSimulatorControl,facebook/FBSimulatorControl