Various test fixes for IMultiCommitStorage

src/ZODB/tests/IExternalGC.test

@@ -46,7 +46,7 @@ transaction ourselves.
     >>> storage.deleteObject(oid0, s0, txn)
     >>> storage.deleteObject(oid1, s1, txn)
     >>> storage.tpc_vote(txn)
-    >>> storage.tpc_finish(txn)
+    >>> _ = storage.tpc_finish(txn)
     >>> tid = storage.lastTransaction()
 
 Now if we try to load data for the objects, we get a POSKeyError:

src/ZODB/tests/TransactionalUndoStorage.py

@@ -111,7 +111,12 @@ def _begin_undos_vote(self, t, *tids):
             undo_result = self._storage.undo(tid, t)
             if undo_result:
                 oids.extend(undo_result[1])
-        oids.extend(oid for (oid, _) in self._storage.tpc_vote(t) or ())
+        v = self._storage.tpc_vote(t)
+        if v:
+            if isinstance(v[0], bytes):
+                oids.extend(v)
+            else:
+                oids.extend(oid for (oid, _) in v)
         return oids
 
     def undo(self, tid, note):

src/ZODB/tests/blob_transaction.txt

@@ -390,10 +390,6 @@ stored are discarded.
     ...                             '', t)
 
     >>> serials = blob_storage.tpc_vote(t)
-    >>> if s1 is None:
-    ...     s1 = [s for (oid, s) in serials if oid == blob._p_oid][0]
-    >>> if s2 is None:
-    ...     s2 = [s for (oid, s) in serials if oid == new_oid][0]
 
     >>> blob_storage.tpc_abort(t)
 
@@ -402,14 +398,7 @@ Now, the serial for the existing blob should be the same:
     >>> blob_storage.load(blob._p_oid, '') == (olddata, oldserial)
     True
 
-And we shouldn't be able to read the data that we saved:
-
-    >>> blob_storage.loadBlob(blob._p_oid, s1)
-    Traceback (most recent call last):
-    ...
-    POSKeyError: 'No blob file at <BLOB STORAGE PATH>'
-
-Of course the old data should be unaffected:
+The old data should be unaffected:
 
     >>> with open(blob_storage.loadBlob(blob._p_oid, oldserial)) as fp:
     ...     fp.read()
@@ -422,11 +411,6 @@ Similarly, the new object wasn't added to the storage:
     ...
     POSKeyError: 0x...
 
-    >>> blob_storage.loadBlob(blob._p_oid, s2)
-    Traceback (most recent call last):
-    ...
-    POSKeyError: 'No blob file at <BLOB STORAGE PATH>'
-
 .. clean up
 
     >>> tm1.abort()