Catch DBus exceptions on class initialization

I came across this:

Traceback (most recent call last):
  File "/tmp/ansible_BhXpTE/ansible_module_openshift_facts.py", line 2409, in <module>
    main()
  File "/tmp/ansible_BhXpTE/ansible_module_openshift_facts.py", line 2396, in main
    protected_facts_to_overwrite)
  File "/tmp/ansible_BhXpTE/ansible_module_openshift_facts.py", line 1855, in __init__
    protected_facts_to_overwrite)
  File "/tmp/ansible_BhXpTE/ansible_module_openshift_facts.py", line 1892, in generate_facts
    defaults = self.get_defaults(roles, deployment_type, deployment_subtype)
  File "/tmp/ansible_BhXpTE/ansible_module_openshift_facts.py", line 1989, in get_defaults
    version_info = get_docker_version_info()
  File "/tmp/ansible_BhXpTE/ansible_module_openshift_facts.py", line 1290, in get_docker_version_info
    if is_service_running('docker'):
  File "/tmp/ansible_BhXpTE/ansible_module_openshift_facts.py", line 1249, in is_service_running
    bus = SystemBus()
  File "/usr/lib64/python2.7/site-packages/dbus/_dbus.py", line 194, in __new__
    private=private)
  File "/usr/lib64/python2.7/site-packages/dbus/_dbus.py", line 100, in __new__
    bus = BusConnection.__new__(subclass, bus_type, mainloop=mainloop)
  File "/usr/lib64/python2.7/site-packages/dbus/bus.py", line 122, in __new__
    bus = cls._new_for_bus(address_or_type, mainloop=mainloop)
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.FileNotFound: Failed to connect to socket /var/run/dbus/system_bus_socket: No such file or directory

roles/openshift_facts/library/openshift_facts.py

@@ -1246,10 +1246,10 @@ def build_api_server_args(facts):
 def is_service_running(service):
     """ Queries systemd through dbus to see if the service is running """
     service_running = False
-    bus = SystemBus()
-    systemd = bus.get_object('org.freedesktop.systemd1', '/org/freedesktop/systemd1')
-    manager = Interface(systemd, dbus_interface='org.freedesktop.systemd1.Manager')
     try:
+        bus = SystemBus()
+        systemd = bus.get_object('org.freedesktop.systemd1', '/org/freedesktop/systemd1')
+        manager = Interface(systemd, dbus_interface='org.freedesktop.systemd1.Manager')
         service_unit = service if service.endswith('.service') else manager.GetUnit('{0}.service'.format(service))
         service_proxy = bus.get_object('org.freedesktop.systemd1', str(service_unit))
         service_properties = Interface(service_proxy, dbus_interface='org.freedesktop.DBus.Properties')
@@ -1258,6 +1258,8 @@ def is_service_running(service):
         if service_load_state == 'loaded' and service_active_state == 'active':
             service_running = True
     except DBusException:
+        # TODO: do not swallow exception, as it may be hiding useful debugging
+        # information.
         pass
 
     return service_running