Bugzilla

The documentation mentions that when you start ingesting pushes or jobs you will know what exchange you're mounted to:
https://github.com/mozilla/treeherder/blob/master/docs/pulseload.md#3-read-pushes

Quote:
> You will see a list of the exchanges it has mounted to and a message for each push as it is read.

I can't see this to be the case:
```bash
root@2c14ad4a3716:/app# ./manage.py pulse_listener_jobs
/app/treeherder/etl/schema.py:13: YAMLLoadWarning: calling yaml.load() without Loader=... is deprecated, as the default Loader is unsafe. Please read https://msg.pyyaml.org/load for full details.
  schema = yaml.load(f)
/usr/local/lib/python3.7/site-packages/rest_framework/exceptions.py:18: DeprecationWarning: 'version' is deprecated. Use '__version__' instead.
  from rest_framework.compat import unicode_to_repr
```

If a user tries to follow the Pulse instructions and uses the wrong credentials the command to ingest will not fail. It will just do nothing.

I'm happy to fix this with some direction.

```bash
root@2c14ad4a3716:/app# ./manage.py pulse_listener_jobs
/app/treeherder/etl/schema.py:13: YAMLLoadWarning: calling yaml.load() without Loader=... is deprecated, as the default Loader is unsafe. Please read https://msg.pyyaml.org/load for full details.
  schema = yaml.load(f)
/usr/local/lib/python3.7/site-packages/rest_framework/exceptions.py:18: DeprecationWarning: 'version' is deprecated. Use '__version__' instead.
  from rest_framework.compat import unicode_to_repr
```