Avoid problems in removing cache managers introduced in Zope 2.12.8.

doc/CHANGES.rst

@@ -11,6 +11,8 @@ http://docs.zope.org/zope2/releases/.
 Bugs Fixed
 ++++++++++
 
+- Avoid problems in removing cache managers introduced in Zope 2.12.8.
+
 - LP #143531: Fix broken object so they give access to their state.
 
 - LP #578326: Issue a warning if someone specifies a non-public permission

src/Products/StandardCacheManagers/AcceleratedHTTPCacheManager.py

@@ -174,7 +174,7 @@ class AcceleratedHTTPCacheManager (CacheManager, SimpleItem):
 
     security.declarePrivate('_remove_data')
     def _remove_data(self):
-        caches.pop(self.__cacheid)
+        caches.pop(self.__cacheid, None)
 
     security.declarePrivate('_resetCacheId')
     def _resetCacheId(self):

src/Products/StandardCacheManagers/RAMCacheManager.py

@@ -382,7 +382,7 @@ class RAMCacheManager (CacheManager, SimpleItem):
 
     security.declarePrivate('_remove_data')
     def _remove_data(self):
-        caches.pop(self.__cacheid)
+        caches.pop(self.__cacheid, None)
 
     security.declarePrivate('_resetCacheId')
     def _resetCacheId(self):