openshift inventory plugin: fix exception when auth fails (#45826)

* openshift inventory: fix exception when auth fails

Fix 'ForbiddenError' object has no attribute 'message':

    [WARNING]:  * Failed to parse test.yml with openshift plugin: 'ForbiddenError' object has no attribute 'message'
     File "ansible/lib/ansible/inventory/manager.py", line 270, in parse_source
       plugin.parse(self._inventory, self._loader, source, cache=cache)
     File "ansible/lib/ansible/plugins/inventory/openshift.py", line 122, in parse
       self.setup(config_data, cache, cache_key)
     File "ansible/lib/ansible/module_utils/k8s/inventory.py", line 58, in setup
       self.fetch_objects(connections)
     File "ansible/lib/ansible/module_utils/k8s/inventory.py", line 250, in fetch_objects
       super(OpenShiftInventoryHelper, self).fetch_objects(connections)
     File "ansible/lib/ansible/module_utils/k8s/inventory.py", line 81, in fetch_objects
       namespaces = self.get_available_namespaces(client)
     File "ansible/lib/ansible/module_utils/k8s/inventory.py", line 95, in get_available_namespaces
       raise K8sInventoryException('Error fetching Namespace list: {0}'.format(exc.message))

Don't try to get 'message' attribute from:
- K8sInventoryException instances
- Exception instances
- KubernetesException instances (because KubernetesException can be
  Exception)

* move k8s/OpenShift inventory plugin dedicated code

inventory plugin specific code should not be located in
lib/ansible/module_utils directory. Then ansible.utils methods can be
reused (for example Display).

* Remove unused class variables 'helper'

unused since 4d77878654.

lib/ansible/module_utils/k8s/scale.py

@@ -70,7 +70,7 @@ class KubernetesAnsibleScaleModule(KubernetesRawModule):
             existing = resource.get(name=name, namespace=namespace)
             return_attributes['result'] = existing.to_dict()
         except KubernetesException as exc:
-            self.fail_json(msg='Failed to retrieve requested object: {0}'.format(exc.message),
+            self.fail_json(msg='Failed to retrieve requested object: {0}'.format(exc),
                            error=exc.value.get('status'))
 
         if self.kind == 'job':
@@ -129,7 +129,7 @@ class KubernetesAnsibleScaleModule(KubernetesRawModule):
             resource.scale.patch(body=scale_obj)
         except Exception as exc:
             self.fail_json(
-                msg="Scale request failed: {0}".format(exc.message)
+                msg="Scale request failed: {0}".format(exc)
             )
 
         if wait and stream is not None:
@@ -173,7 +173,7 @@ class KubernetesAnsibleScaleModule(KubernetesRawModule):
                             watcher.stop()
                             break
         except Exception as exc:
-            self.fail_json(msg="Exception reading event stream: {0}".format(exc.message))
+            self.fail_json(msg="Exception reading event stream: {0}".format(exc))
 
         if not return_obj:
             self.fail_json(msg="Error fetching the patched object. Try a higher wait_timeout value.")