only happens when the class defines a custom __getattr__:

>>> class Foo(object):
...     def __getattr__(self, name):
...         if name == "spam":
...             return 17
...         else:
...             raise AttributeError("%s object has no attribute %r" %
...                 (self.__class__.__name__, name))
...     @property
...     def bacon(self):
...         return int.lalala
...
>>>
>>> f = Foo()
>>> f.spam
17
>>> f.bacon
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 7, in __getattr__
AttributeError: Foo object has no attribute 'bacon'  <<-- expected 'int object has no attribute lalala'
>>>

----------------------------------------------------

without a custom __getattr__ works as expected

>>> class Bar(object):
...     def __init__(self):
...         self.x = 17
...
...     @property
...     def bacon(self):
...         return int.lalala
...
>>> b = Bar()
>>> b.x
17
>>> b.bacon
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 7, in bacon
AttributeError: type object 'int' has no attribute 'lalala'
>>>