fuel-cli throws trace instead of error message

[Tomasz 'Zen' Napierala]

When using cli on master node and when api container is down, fuel-cli instead of pretty error message throws :
[root@fuel ~]# fuel provisioning --env-id 1 --default -d
Traceback (most recent call last):
  File "/usr/bin/fuel", line 9, in <module>
    load_entry_point('fuelclient==0.2', 'console_scripts', 'fuel')()
  File "/usr/lib/python2.6/site-packages/pkg_resources.py", line 299, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/usr/lib/python2.6/site-packages/pkg_resources.py", line 2229, in load_entry_point
    return ep.load()
  File "/usr/lib/python2.6/site-packages/pkg_resources.py", line 1948, in load
    entry = __import__(self.module_name, globals(),globals(), ['__name__'])
  File "/usr/lib/python2.6/site-packages/fuelclient/cli/parser.py", line 18, in <module>
    from fuelclient.cli.actions import actions
  File "/usr/lib/python2.6/site-packages/fuelclient/cli/actions/__init__.py", line 19, in <module>
    from fuelclient.cli.actions.deploy import DeployChangesAction
  File "/usr/lib/python2.6/site-packages/fuelclient/cli/actions/deploy.py", line 16, in <module>
    from fuelclient.cli.actions.base import Action
  File "/usr/lib/python2.6/site-packages/fuelclient/cli/actions/base.py", line 22, in <module>
    from fuelclient.client import APIClient
  File "/usr/lib/python2.6/site-packages/fuelclient/client.py", line 190, in <module>
    APIClient = Client()
  File "/usr/lib/python2.6/site-packages/fuelclient/client.py", line 60, in __init__
    self.auth_status()
  File "/usr/lib/python2.6/site-packages/fuelclient/client.py", line 83, in auth_status
    request = urllib2.urlopen(''.join([self.api_root, 'version']))
  File "/usr/lib64/python2.6/urllib2.py", line 126, in urlopen
    return _opener.open(url, data, timeout)
  File "/usr/lib64/python2.6/urllib2.py", line 391, in open
    response = self._open(req, data)
  File "/usr/lib64/python2.6/urllib2.py", line 409, in _open
    '_open', req)
  File "/usr/lib64/python2.6/urllib2.py", line 369, in _call_chain
    result = func(*args)
  File "/usr/lib64/python2.6/urllib2.py", line 1190, in http_open
    return self.do_open(httplib.HTTPConnection, req)
  File "/usr/lib64/python2.6/urllib2.py", line 1165, in do_open
    raise URLError(err)
urllib2.URLError: <urlopen error [Errno 111] Connection refused>

[Sebastian Kalinowski (prmtl)]

https://review.openstack.org/#/c/107357/ introduced nice error message:

[root@fuel ~]# dockerctl stop nginx
[root@fuel ~]# fuel provisioning --env-id 1 --default

            Can't connect to Nailgun server!
            Please modify "SERVER_ADDRESS" and "LISTEN_PORT"
            in the file /etc/fuel/client/config.yaml