In checkReconnectSwitch(), during the switch, _dostore() can fail with

a variety of exceptions.  Catch all of them.  (The only ones I've seen
are Disconnected and ReadOnlyError, but since we're disconnected
abruptly as part of the switch, it's possible to see any of the
exceptions that checkReconnection() catches.)

src/ZEO/tests/testZEO.py

@@ -508,7 +508,8 @@ class ConnectionTests(StorageTestBase.StorageTestBase):
             try:
                 self._dostore()
                 break
-            except ReadOnlyError:
+            except (Disconnected, ReadOnlyError,
+                    select.error, thread.error, socket.error):
                 time.sleep(0.1)
         else:
             self.fail("Couldn't store after starting a read-write server")