Error: Connection ended: possibly due to an authentication failure

I'm running amqp-tool against rabbitmq 3.2.4 using an authenticated user but always fails. Logging in the web UI works though:
```
amqp-tool -vvvv --host localhost --port 32781 -u jgaspar -p 123456 -q test --count 1 --export dump.json
RabbitMQ :: error Error: Connection ended: possibly due to an authentication failure.
at Connection. (/usr/lib/node_modules/amqp-tool/node_modules/amqp/lib/connection.js:283:26)
at emitNone (events.js:106:13)
at Connection.emit (events.js:208:7)
at emitNone (events.js:111:20)
at Socket.emit (events.js:208:7)
at endReadableNT (_stream_readable.js:1064:12)
at _combinedTickCallback (internal/process/next_tick.js:138:11)
at process._tickCallback (internal/process/next_tick.js:180:9)
RabbitMQ connection closed :: close false
```

When not specifying a user it works fine with default one (guest/guest). Rabbitmq is running inside a vagrant box and I'm forwarding the port, hence it's using 32781.

---
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