Collector #1515: 2.8 failure: Cache statistics do not work

The DB.cacheStatistics() method was introduced in DB.py rev 1.2,
and has always returned an empty tuple.  A number of "never did
anything, probably never will" DB methods like that were removed
in ZODB 3.3, to reduce stumbling over decoys.  That was discussed
on zodb-dev at the time, with universal agreement to get rid of
them.

So the resolution in this case is changing Zope to stop trying
to access the no-longer-extant cacheStatistics() method.  If
someone doesn't like this, they can revert this patch, then
change App/CacheManager.py's cacheStatistics() to return a
hard coded empty tuple <wink>.

lib/python/App/CacheManager.py

@@ -92,9 +92,6 @@ class CacheManager:
             response.redirect(REQUEST['URL1']+'/manage_cacheParameters')
 
 
-    def cacheStatistics(self):
-        return self._getDB().cacheStatistics()
-
     # BoboPOS 2
     def cache_mean_age(self):
         return Globals.Bobobase._jar.cache.cache_mean_age/60.0

lib/python/App/dtml/cacheGC.dtml

@@ -27,19 +27,6 @@
 </table>
 
 
-<dtml-if cacheStatistics>
-<h3>Cache Statistics</h3>
-<table>
-
-<dtml-in cacheStatistics>
-<tr><th align=left>&dtml-sequence-key;</th>
-    <td>&dtml-sequence-item;</td>
-</tr>
-</dtml-in>
-
-</table>
-</dtml-if>
-
 <dtml-if show_cache_detail>
   <h4>Cache Details</h4><P>
 

lib/python/App/dtml/cacheParameters.dtml

@@ -41,18 +41,6 @@
   </td>
 </tr>
 
-
-<dtml-in cacheStatistics>
-<tr>
-  <th align=left>
-  &dtml-sequence-key;
-  </th>
-  <td>
-  &dtml-sequence-item;
-  </td>
-</tr>
-</dtml-in>
-
 <tr>
   <td align="left" colspan=2>
   <div class="form-label">