The newer checkPackVersionReachable() test must fail when using

a MappingStorage (which doesn't support versions), so stop trying to
test that combo.

src/ZEO/tests/testZEO.py

@@ -220,6 +220,7 @@ class MappingStorageTests(FileStorageTests):
     def checkPackEmptyStorage(self): pass
     def checkPackAllRevisions(self): pass
     def checkPackVersionsInPast(self): pass
+    def checkPackVersionReachable(self): pass
     def checkNotUndoable(self): pass
     def checkNewSerialOnCommitVersionToVersion(self): pass
     def checkModifyAfterAbortVersion(self): pass