That makes 3.0 crash.

This was apparantly fixed in 3.1, so I imagine py-dev knows about it--I'm not
sure it's entirely wise, anyways. I'm thinking about finding the places that use
Nested() and getting rid of them.

Author: James William Pye

postgresql/python/contextlib.py

@@ -66,10 +66,8 @@ def __exit__(self, typ, val, tb):
 					typ = val = tb = None
 			except:
 				newtyp, newval, newtb = sys.exc_info()
-				if getattr(newval,'__cause__') is None:
-					newval.__cause__ = getattr(newval, '__context__', val)
-				if newval.__cause__ is newval.__context__:
-					newval.__context__ = None
+				if newval.__cause__ is None:
+					newval.__cause__ = newval.__context__
 				typ = newtyp
 				val = newval
 				tb = newtb