Fix issue in pywbem_mock with incorrect error response to invokemethod

We need to return something like NOT_SUPPORTED when there are no methods
in the methods repo. The code was returning NOT_FOUND.  This was causing
issues with the get_central_instances test.

pywbem_mock/_wbemconnection_mock.py

@@ -1449,6 +1449,8 @@ def _fake_createclass(self, namespace, **params):
 
         if namespace not in self.classes:
             self.classes[namespace] = NocaseDict({})
+            if namespace not in self.methods:
+                self.methods[namespace] = NocaseDict()
 
         if new_class.classname in self.classes[namespace]:
             raise CIMError(CIM_ERR_ALREADY_EXISTS,
@@ -1829,6 +1831,8 @@ def _fake_createinstance(self, namespace, **params):
             self.instances[namespace].append(new_instance)
         except KeyError:
             self.instances[namespace] = [new_instance]
+            if namespace not in self.methods:
+                self.methods[namespace] = NocaseDict()
 
         # Create instance returns model path, path relative to namespace
         return self._make_tuple([new_instance.path.copy()])
@@ -2913,9 +2917,21 @@ def _fake_invokemethod(self, methodname, objectname, Params, **params):
         namespace = localobject.namespace
         try:
             methodsrepo = self._get_methods_repo(namespace)
+        except CIMError as ce:
+            # If invoke indicates method repo not built, create it.
+            if ce.status_code == CIM_ERR_INVALID_NAMESPACE:
+                if namespace in self.classes or \
+                        namespace in self.instances:
+                    raise CIMError(CIM_ERR_NOT_SUPPORTED,
+                                   'Method %s in namespace %s not registered '
+                                   'in repository' %
+                                   (methodname, namespace))
+                else:
+                    raise
         except KeyError:
-            raise CIMError(CIM_ERR_NOT_FOUND, 'Method %s in namespace %s not '
-                                              'registered in repository' %
+            raise CIMError(CIM_ERR_NOT_SUPPORTED,
+                           'Method %s in namespace %s not registered in '
+                           'repository' %
                            (methodname, namespace))
 
         # find the methods entry corresponding to classname. It must be in