Allow get_class_name to accept bound method and class method

It is convenient in some cases like:
  if inspect.ismethod(callback):
    class_name = callback.__self__.__class__.__name__
    return [module_name, class_name, func_name]
  else:
    return [module_name, func_name]

The above code example from keystone [1]
[1] https://github.com/openstack/keystone/blob/master/keystone/notifications.py#L256

Change-Id: I4f90c70e8838a1fccb51856b461780ba5fce06d4

oslo_utils/reflection.py

@@ -56,10 +56,19 @@ def get_member_names(obj, exclude_hidden=True):
 def get_class_name(obj, fully_qualified=True):
     """Get class name for object.
 
-    If object is a type, fully qualified name of the type is returned.
-    Else, fully qualified name of the type of the object is returned.
-    For builtin types, just name is returned.
+    If object is a type, returns name of the type. If object is a bound
+    method or a class method, returns its ``self`` object's class name.
+    If object is an instance of class, returns instance's class name.
+    Else, name of the type of the object is returned. If fully_qualified
+    is True, returns fully qualified name of the type. For builtin types,
+    just name is returned. TypeError is raised if can't get class name from
+    object.
     """
+    if inspect.isfunction(obj):
+        raise TypeError("Can't get class name.")
+
+    if inspect.ismethod(obj):
+        obj = get_method_self(obj)
     if not isinstance(obj, six.class_types):
         obj = type(obj)
     try:

oslo_utils/tests/test_reflection.py

@@ -321,6 +321,30 @@ class GetClassNameTest(test_base.BaseTestCase):
         name = reflection.get_class_name(42)
         self.assertEqual('int', name)
 
+    def test_class_method(self):
+        name = reflection.get_class_name(Class.class_method)
+        self.assertEqual('%s.Class' % __name__, name)
+        # test with fully_qualified=False
+        name = reflection.get_class_name(Class.class_method,
+                                         fully_qualified=False)
+        self.assertEqual('Class', name)
+
+    def test_static_method(self):
+        self.assertRaises(TypeError, reflection.get_class_name,
+                          Class.static_method)
+
+    def test_unbound_method(self):
+        self.assertRaises(TypeError, reflection.get_class_name,
+                          mere_function)
+
+    def test_bound_method(self):
+        c = Class()
+        name = reflection.get_class_name(c.method)
+        self.assertEqual('%s.Class' % __name__, name)
+        # test with fully_qualified=False
+        name = reflection.get_class_name(c.method, fully_qualified=False)
+        self.assertEqual('Class', name)
+
 
 class GetAllClassNamesTest(test_base.BaseTestCase):