Python supports a limited form of multiple inheritance. In what way limited?

Question

In the python tutorial it's said that "Python supports a limited form of multiple inheritance".

What are the limitations?

Answer 1

Apart from @Matt Anderson's answer I think that the limitations is in fact for the old style classes (which the tutorial for Python 2.6 still addresses).

In the Python 3 tutorial the text is now: Python supports a form of multiple inheritance as well.