Description:
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Currently (stomp 1.0.5) doesn't parse or look for ERROR response frames when doing CONNECT. 
See here: https://github.com/php/pecl-tools-stomp/blob/master/php_stomp.c#L552

Should probably do something similar to: https://github.com/php/pecl-tools-stomp/blob/master/php_stomp.c#L893

When running Stomp against AMQP according to http://activemq.apache.org/stomp.html :
Stomp implementation fully supports an ActiveMQ security mechanism. This means that the CONNECT command will return an ERROR frame on unsuccessful authentication

This is on par with http://stomp.github.io/stomp-specification-1.1.html#Connecting

Expected result:
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StompException containing the error message.

Actual result:
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StompException: Stomp unknown error