Fix small bug that the Connection.isReadOnly method did not work after a savepoint

NEWS.txt

@@ -34,6 +34,8 @@ General
   on datetimes or serials (TIDs).  See
   src/ZODB/historical_connections.txt.
   
+- (3.9.0a1) Fixed small bug that the Connection.isReadOnly method didn't
+  work after a savepoint.
 
 ZEO
 ---

src/ZODB/Connection.py

@@ -1175,6 +1175,7 @@ class TmpStore:
         self._storage = storage
         for method in (
             'getName', 'new_oid', 'getSize', 'sortKey', 'loadBefore',
+            'isReadOnly'
             ):
             setattr(self, method, getattr(storage, method))
 

src/ZODB/component.xml

@@ -182,8 +182,8 @@
       </description>
     <key name="historical-pool-size" datatype="integer" default="3"/>
       <description>
-        The expected maximum number of connections simultaneously open
-        per historical revision.
+        The expected maximum total number of historical connections
+        simultaneously open.
       </description>
     <key name="historical-cache-size" datatype="integer" default="1000"/>
       <description>

src/ZODB/tests/testConnectionSavepoint.py

@@ -138,6 +138,21 @@ Verify all the values are as expected:
     >>> db.close()
 """
 
+def testIsReadonly():
+    """\
+The connection isReadonly method relies on the _storage to have an isReadOnly.
+We simply rely on the underlying storage method.
+
+    >>> import ZODB.tests.util
+    >>> db = ZODB.tests.util.DB()
+    >>> connection = db.open()
+    >>> root = connection.root()
+    >>> root['a'] = 1
+    >>> sp = transaction.savepoint()
+    >>> connection.isReadOnly()
+    False
+"""
+
 def test_suite():
     return unittest.TestSuite((
         doctest.DocFileSuite('testConnectionSavepoint.txt'),