CFNetworkHandler is not a valid http message handler for watchOS, so show a helpful message if someone tries. (#879)

docs/website/mtouch-errors.md

@@ -837,7 +837,7 @@ This generally indicates that there is a problem with your Xamarin.iOS installat
 
 <!--- 2012 used by mmp -->
 
-<h3><a name="MT2015"/>MT2015: Invalid HttpMessageHandler `*` for watchOS. Valid values are NSUrlSessionHandler (default) or CFNetworkHandler</h3>
+<h3><a name="MT2015"/>MT2015: Invalid HttpMessageHandler `*` for watchOS. The only valid value is NSUrlSessionHandler.</h3>
 
 <!--
  MT3xxx AOT

src/ObjCRuntime/RuntimeOptions.cs

@@ -66,11 +66,11 @@ namespace XamCore.ObjCRuntime {
 			// default
 			case null:
 				return HttpClientHandlerValue;
+			case CFNetworkHandlerValue:
 			case HttpClientHandlerValue:
 				if (Driver.App.Platform == Utils.ApplePlatform.WatchOS)
-					throw ErrorHelper.CreateError (2015, "Invalid HttpMessageHandler `{0}` for watchOS. Valid values are NSUrlSessionHandler (default) or CFNetworkHandler", value);
+					throw ErrorHelper.CreateError (2015, "Invalid HttpMessageHandler `{0}` for watchOS. The only valid value is NSUrlSessionHandler.", value);
 				return value;
-			case CFNetworkHandlerValue:
 			case NSUrlSessionHandlerValue:
 				return value;
 			default:
@@ -186,10 +186,12 @@ namespace XamCore.ObjCRuntime {
 #else
 			case HttpClientHandlerValue:
 				if (Driver.App.Platform == Utils.ApplePlatform.WatchOS)
-					throw ErrorHelper.CreateError (2015, "Invalid HttpMessageHandler `{0}` for watchOS. Valid values are NSUrlSessionHandler (default) or CFNetworkHandler", handler);
+					throw ErrorHelper.CreateError (2015, "Invalid HttpMessageHandler `{0}` for watchOS. The only valid value is NSUrlSessionHandler.", handler);
 				type = httpModule.GetType ("System.Net.Http", "HttpClientHandler");
 				break;
 			case CFNetworkHandlerValue:
+				if (Driver.App.Platform == Utils.ApplePlatform.WatchOS)
+					throw ErrorHelper.CreateError (2015, "Invalid HttpMessageHandler `{0}` for watchOS. The only valid value is NSUrlSessionHandler.", handler);
 				type = httpModule.GetType ("System.Net.Http", "CFNetworkHandler");
 				break;
 			case NSUrlSessionHandlerValue:

tools/mtouch/error.cs

@@ -204,7 +204,7 @@ namespace Xamarin.Bundler {
 	//					MT2012  ** reserved Xamarin.Mac **
 	//					MT2013	** reserved Xamarin.Mac **
 	//					MT2014	** reserved Xamarin.Mac **
-	//					MT2015	Invalid HttpMessageHandler `{0}` for watchOS. Valid values are NSUrlSessionHandler (default) or CFNetworkHandler
+	//					MT2015	Invalid HttpMessageHandler `{0}` for watchOS. The only valid value is NSUrlSessionHandler.
 	// MT3xxx	AOT
 	//			MT30xx	AOT (general) errors
 	//					MT3001	Could not AOT the assembly '{0}'