The bug seems related to Sphynx on Python3.

These examples are NOT colored::

  class Z:
    def __init__(self):
      pass

::

  class F:
    def __foo__(self):
      pass

::

  class C:
      def method(self):
          pass

  c = C()
  c.method.__func__.whoami = 'my name is c'



While these examples are colored correctly::

  class A:
    pass

  class B:
    def b(self):
      pass

  class C(): pass