Don't raise AttributeError for '__iter__' if fallback to '__getitem__' succeeds.

LP #1155760.

Cherry-pick 7b5c5fd1 from master.

CHANGES.txt

 Changelog
 =========
 
+2.13.9 (unreleased)
+-------------------
+
+- Don't raise an attribute error for ``__iter__`` if the fallback to
+  ``__getitem__`` succeeds.  LP #1155760.
+
 2.13.8 (2011-06-11)
 -------------------
 

src/Acquisition/_Acquisition.c

@@ -984,6 +984,7 @@ Wrapper_iter(Wrapper *self)
           res = NULL;
       }
   } else if (PySequence_Check(obj)) {
+      PyErr_Clear();
       ASSIGN(res,PySeqIter_New(OBJECT(self)));
   } else {
       res = PyErr_Format(PyExc_TypeError, "iteration over non-sequence");

src/Acquisition/tests.py

@@ -2397,6 +2397,24 @@ def test___parent__aq_parent_circles():
     """
 
 
+def test__iter__after_AttributeError():
+    """ See https://bugs.launchpad.net/zope2/+bug/1155760
+
+    >>> from Acquisition import Implicit
+    >>> class C(Implicit):
+    ...     l = [0, 1, 2, 3, 4]
+    ...     def __getitem__(self, i):
+    ...         return self.l[i]
+    >>> a = C()
+    >>> b = C().__of__(a)
+    >>> import time
+    >>> try:
+    ...     for n in b:
+    ...         t = time.gmtime()
+    ... except AttributeError:
+    ...     raise
+    """
+
 import unittest
 from doctest import DocTestSuite, DocFileSuite