Merge pull request #4532 from takluyver/sphinx-1.2-dynamic-metaclasses

Hide dynamically defined metaclass base from Sphinx.

IPython/utils/py3compat.py

@@ -239,4 +239,4 b' else:'
 
 def with_metaclass(meta, *bases):
     """Create a base class with a metaclass."""
-    return meta("NewBase", bases, {})
+    return meta("_NewBase", bases, {})