Verify the presence of dbus python binding

While the proper fix is to have it installed by default, this commit
will also permit to have a better error message in the case the module
is not present (as running on python 3)

roles/openshift_facts/library/openshift_facts.py

@@ -22,9 +22,14 @@ from distutils.util import strtobool
 from distutils.version import LooseVersion
 import struct
 import socket
-from dbus import SystemBus, Interface
-from dbus.exceptions import DBusException
 
+HAVE_DBUS=False
+try:
+    from dbus import SystemBus, Interface
+    from dbus.exceptions import DBusException
+    HAVE_DBUS=True
+except ImportError:
+    pass
 
 DOCUMENTATION = '''
 ---
@@ -2277,6 +2282,9 @@ def main():
         add_file_common_args=True,
     )
 
+    if not HAVE_DBUS:
+        module.fail_json(msg="This module requires dbus python bindings")
+
     module.params['gather_subset'] = ['hardware', 'network', 'virtual', 'facter']
     module.params['gather_timeout'] = 10
     module.params['filter'] = '*'