message: mark as abstract
diff: @@ -12,7 +12,7 @@ import { Lib_ReentrancyGuard } from "../../libraries/utils/Lib_ReentrancyGuard.s
  /**
  * @title OVM_BaseCrossDomainMessenger
  */
  -contract OVM_BaseCrossDomainMessenger is iOVM_BaseCrossDomainMessenger, Lib_ReentrancyGuard {
  +abstract contract OVM_BaseCrossDomainMessenger is iOVM_BaseCrossDomainMessenger, Lib_ReentrancyGuard {
  /**********************
  * Contract Variables *
  @@ -28,7 +28,7 @@ contract OVM_BaseCrossDomainMessenger is iOVM_BaseCrossDomainMessenger, Lib_Reen
  * Public Functions *
  ********************/
  - constructor() Lib_ReentrancyGuard() public {}
  + constructor() Lib_ReentrancyGuard() internal {}
  /**
  * Sends a cross domain message to the target messenger.
  