No suitable request handler found

config.tx_extbase {
 objects {
  Tx_Extbase_Persistence_Storage_BackendInterface {
   className = Tx_Extbase_Persistence_Storage_Typo3DbBackend
  }
 }
 mvc {
  requestHandlers {
   Tx_Extbase_MVC_Web_FrontendRequestHandler = Tx_Extbase_MVC_Web_FrontendRequestHandler
   Tx_Extbase_MVC_Web_BackendRequestHandler = Tx_Extbase_MVC_Web_BackendRequestHandler
  }
 }
}