Remove __providesBy__ attribute from being copied

This change reverts part of what
https://github.com/Pylons/pyramid/issues/1212 changed. We attempt to
copy information used by zope.interfaces to the new class to avoid
creating new objects that could possibly leak.

Unfortunately copying over __providedBy__ causes issues with the
sub-class after modification no longer implementing interfaces, for more
information see:
https://github.com/Pylons/pyramid/issues/1529#issuecomment-73373581

Once __providedBy__ is removed from the list, this is no longer the case
and the new class that is created in `_set_properties` properly report
that it implements the interfaces it used to implement before.

2 files changed, 5 insertions, 6 deletions

diff --git a/pyramid/tests/test_request.py b/pyramid/tests/test_request.py
index 1a7b1a106..091454893 100644
--- a/pyramid/tests/test_request.py
+++ b/pyramid/tests/test_request.py
@@ -436,7 +436,6 @@ class Test_call_app_with_subpath_as_path_info(unittest.TestCase):
         self.assertEqual(request.environ['PATH_INFO'], '/' + encoded)
 
 class Test_subclassing_Request(unittest.TestCase):
-
     def test_subclass(self):
         from pyramid.interfaces import IRequest
         from pyramid.request import Request
diff --git a/pyramid/util.py b/pyramid/util.py
index 18cef4602..7903326a5 100644
--- a/pyramid/util.py
+++ b/pyramid/util.py
@@ -87,10 +87,10 @@ class InstancePropertyMixin(object):
         if attrs:
             parent = self.__class__
             cls = type(parent.__name__, (parent, object), attrs)
-            # We assign __provides__, __implemented__ and __providedBy__ below
-            # to prevent a memory leak that results from from the usage of this
-            # instance's eventual use in an adapter lookup.  Adapter lookup
-            # results in ``zope.interface.implementedBy`` being called with the
+            # We assign __provides__ and __implemented__ below to prevent a
+            # memory leak that results from from the usage of this instance's
+            # eventual use in an adapter lookup.  Adapter lookup results in
+            # ``zope.interface.implementedBy`` being called with the
             # newly-created class as an argument.  Because the newly-created
             # class has no interface specification data of its own, lookup
             # causes new ClassProvides and Implements instances related to our
@@ -99,7 +99,7 @@ class InstancePropertyMixin(object):
             # want this new class to behave exactly like it is the parent class
             # instead.  See https://github.com/Pylons/pyramid/issues/1212 for
             # more information.
-            for name in ('__implemented__', '__providedBy__', '__provides__'):
+            for name in ('__implemented__', '__provides__'):
                 # we assign these attributes conditionally to make it possible
                 # to test this class in isolation without having any interfaces
                 # attached to it