Fix Implementation to use correct C function and add test.

`Wrapper_str` is needed for Python 2 as it does not have a `PyBytes_FromObject`.

src/Acquisition/_Acquisition.c

@@ -982,7 +982,11 @@ Wrapper_bytes(Wrapper *self)
         return r;
     } else {
         PyErr_Clear();
+#ifdef PY3K
+        return PyBytes_FromObject(self->obj);
+#else
         return Wrapper_str(self);
+#endif
     }
 }
 

src/Acquisition/__init__.py

@@ -47,7 +47,7 @@ def _apply_filter(predicate, inst, name, result, extra, orig):
     return predicate(orig, inst, name, result, extra)
 
 
-if sys.version_info < (3,):
+if sys.version_info < (3,):  # pragma: PY2
     import copy_reg
 
     def _rebound_method(method, wrapper):
@@ -570,7 +570,7 @@ def __bytes__(self):
         aq_self = self._obj
         try:
             return _rebound_method(aq_self.__bytes__, self)()
-        except (AttributeError, TypeError):  # pragma: no cover (Only Py3)
+        except (AttributeError, TypeError):  # pragma: PY3
             return bytes(aq_self)
 
     __binary_special_methods__ = [

src/Acquisition/tests.py

@@ -2450,7 +2450,7 @@ class Impl(Implicit):
         self.assertIs(type(child.__dict__['child2']), Impl)
 
     @unittest.skipIf(PY2, 'Python 2 has no explicit bytes support')
-    def test__bytes__is_correcty_wrapped(self):
+    def test__bytes__is_correcty_wrapped(self):  # pragma: PY3
         class A(Implicit):
 
             def __bytes__(self):
@@ -2461,6 +2461,17 @@ def __bytes__(self):
         wrapper = Acquisition.ImplicitAcquisitionWrapper(a.b, a)
         self.assertEqual(b'my bytes', bytes(wrapper))
 
+    @unittest.skipIf(PY2, 'Python 2 has no explicit bytes support')
+    def test_AttributeError_if_object_has_no__bytes__(self):  # pragma: PY3
+        class A(Implicit):
+            pass
+
+        a = A()
+        a.b = A()
+        wrapper = Acquisition.ImplicitAcquisitionWrapper(a.b, a)
+        with self.assertRaises(TypeError):
+            bytes(wrapper)
+
 
 class TestOf(unittest.TestCase):