Show yellowbox when we fail to load a local image

Reviewed By: achen1

Differential Revision: D4342295

fbshipit-source-id: 9411ffe9a376e1ed51fcadee718326d1d9443fff

Author: Mehdi Mulani

Libraries/Image/RCTLocalAssetImageLoader.m

@@ -105,6 +105,7 @@ - (RCTImageLoaderCancellationBlock)loadImageForURL:(NSURL *)imageURL
       completionHandler(nil, image);
     } else {
       NSString *message = [NSString stringWithFormat:@"Could not find image named %@", imageName];
+      RCTLogWarn(@"%@", message);
       completionHandler(RCTErrorWithMessage(message), nil);
     }
   });

Libraries/Utilities/RCTLog.js

@@ -33,10 +33,12 @@ class RCTLog {
       logFn,
       'Level "' + level + '" not one of ' + Object.keys(levelsMap)
     );
-    if (typeof global.nativeLoggingHook === 'undefined') {
+    if (typeof global.nativeLoggingHook === 'undefined' || level === 'warn') {
       // We already printed in xcode, so only log here if using a js debugger
+      // or if we're trying to send a yellow box from native down.
       console[logFn].apply(console, args);
     }
+
     return true;
   }
 }