Make all the tests in the w_zodb Tox environment run.

BTrees/tests/common.py

@@ -70,6 +70,11 @@ def _getRoot(self):
         return self.db.open().root()
 
     def _closeRoot(self, root):
+        import transaction
+        # If we don't commit/abort the transaction, then
+        # closing the Connection tends to fail with
+        # "Cannot close connection joined to transaction"
+        transaction.abort()
         root._p_jar.close()
 
     @_skip_wo_ZODB

BTrees/tests/testConflict.py

@@ -24,6 +24,32 @@ def _getTargetClass(self):
         from BTrees.OOBTree import OOBTree
         return OOBTree
 
+    def openDB(self):
+        # The conflict tests tend to open two or more connections
+        # and then try to commit them. A standard FileStorage
+        # is not MVCC aware, and so each connection would have the same
+        # instance of the storage, leading to the error
+        # "Duplicate tpc_begin calls for same transaction" on commit;
+        # thus we use a MVCCMappingStorage for these tests, ensuring each
+        # connection has its own storage.
+        # Unfortunately, it wants to acquire the identically same
+        # non-recursive lock in each of its *its* tpc_* methods, which deadlocks.
+        # The solution is to give each instance its own lock, and trust in the
+        # serialization (ordering) of the datamanager, and the fact that these tests are
+        # single-threaded.
+        import threading
+        from ZODB.tests.MVCCMappingStorage  import MVCCMappingStorage
+        class _MVCCMappingStorage(MVCCMappingStorage):
+            def new_instance(self):
+                inst = MVCCMappingStorage.new_instance(self)
+                inst._commit_lock = threading.Lock()
+                return inst
+        from ZODB.DB import DB
+        self.storage = _MVCCMappingStorage()
+        self.db = DB(self.storage)
+        return self.db
+
+
     @_skip_wo_ZODB
     def testSimpleConflict(self):
         # Invoke conflict resolution by committing a transaction and
@@ -478,7 +504,7 @@ def testConflictWithOneEmptyBucket(self):
 
     @_skip_wo_ZODB
     def testConflictOfInsertAndDeleteOfFirstBucketItem(self):
-        """
+        """ testConflictOfInsertAndDeleteOfFirstBucketItem
         Recently, BTrees became careful about removing internal keys
         (keys in internal aka BTree nodes) when they were deleted from
         buckets. This poses a problem for conflict resolution.