Log guzzle requests in a different channel (and a different file)

config.yml

# http://symfony.com/doc/current/cookbook/logging/channels_handlers.html#switching-a-channel-to-a-different-handler
monolog:
    channels: ["guzzle"]
    handlers:
        main:
            type:     stream
            path:     /var/log/symfony.log
            channels: ["!guzzle"]
        guzzle:
            type:     stream
            path:     /var/log/guzzle.log
            channels: [guzzle]

# http://symfony.com/doc/current/cookbook/logging/channels_handlers.html#configure-additional-channels-without-tagged-services
# https://github.com/csarrazi/CsaGuzzleBundle/blob/master/src/Resources/doc/available_subscribers.md#the-logger-subscriber
csa_guzzle:
    logger:
        enabled: true
        service: monolog.logger.guzzle