adjust ReplaceableWrapper to work in Zope 4

CHANGES.rst

@@ -14,7 +14,8 @@ New features:
 
 Bug fixes:
 
-- *add item here*
+- Fix webdav PUT of index_html to work in Zope 4.
+  [davisagli]
 
 
 1.2.3 (2017-03-27)

src/plone/app/folder/base.py

@@ -12,12 +12,13 @@
 from webdav.NullResource import NullResource
 from zope.interface import implementer
 from App.class_init import InitializeClass
+import Acquisition
 
 # to keep backward compatibility
 has_btree = 1
 
 
-class ReplaceableWrapper:
+class ReplaceableWrapper(Acquisition.Implicit):
     """ a wrapper around an object to make it replaceable """
 
     def __init__(self, ob):
@@ -28,6 +29,9 @@ def __getattr__(self, name):
             return REPLACEABLE
         return getattr(self.__ob, name)
 
+    def __repr__(self):
+        return repr(aq_base(self.__ob))
+
 
 @implementer(IOrderedContainer)
 class BaseBTreeFolder(OrderedBTreeFolderBase, BaseFolder):
@@ -74,8 +78,9 @@ def index_html(self, REQUEST=None, RESPONSE=None):
                 else:
                     raise AttributeError('index_html')
         # Acquire from parent
-        target = aq_parent(aq_inner(self)).aq_acquire('index_html')
-        return ReplaceableWrapper(aq_base(target).__of__(self))
+        parent = aq_parent(aq_inner(self))
+        target = parent.aq_acquire('index_html')
+        return ReplaceableWrapper(aq_base(target)).__of__(parent).__of__(self)
 
     index_html = ComputedAttribute(index_html, 1)