Description of problem:
Traceback thrown when there's a network issue

Version-Release number of selected component (if applicable):
# subscription-manager version
server type: Red Hat Subscription Management
subscription management server: 0.9.2-1
subscription-manager: 1.10.13-1.el7
python-rhsm: 1.10.12-1.el7


How reproducible:
Always

Steps to Reproduce:
1. Open sub-man GUI and Register to candlepin
2. Open preference dialog
3. Shut down the network (systemctl stop network)
4. Try performing an action in the preference window
   (changing "Release Version"/"Service Level")

Actual results:
Traceback is thrown on stdout

Expected results:
An error message should be thrown and it should exit gracefully

Additional info:

Tracebsack:

Traceback (most recent call last):
  File "/usr/share/rhsm/subscription_manager/gui/preferences.py", line 185, in _sla_changed
    service_level=new_sla)
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 794, in updateConsumer
    ret = self.conn.request_put(method, params)
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 563, in request_put
    return self._request("PUT", method, params)
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 457, in _request
    conn.request(request_type, handler, body=body, headers=headers)
  File "/usr/lib64/python2.7/httplib.py", line 973, in request
    self._send_request(method, url, body, headers)
  File "/usr/lib64/python2.7/httplib.py", line 1007, in _send_request
    self.endheaders(body)
  File "/usr/lib64/python2.7/httplib.py", line 969, in endheaders
    self._send_output(message_body)
  File "/usr/lib64/python2.7/httplib.py", line 829, in _send_output
    self.send(msg)
  File "/usr/lib64/python2.7/httplib.py", line 791, in send
    self.connect()
  File "/usr/lib64/python2.7/site-packages/M2Crypto/httpslib.py", line 51, in connect
    socket.getaddrinfo(self.host, self.port, 0, socket.SOCK_STREAM):
socket.gaierror: [Errno -2] Name or service not known