Merge pull request #381 from repodio/throw-on-cancel-android

Cancel download throw error bugfix (Android)

index.js

     return fetchFile(options, method, url, headers, body)
   }
 
+  let promiseResolve;
+  let promiseReject;
+
   // from remote HTTP(S)
   let promise = new Promise((resolve, reject) => {
+    promiseResolve = resolve;
+    promiseReject = reject;
+
     let nativeMethodName = Array.isArray(body) ? 'fetchBlobForm' : 'fetchBlob'
 
     // on progress event listener
     subscriptionUpload.remove()
     stateEvent.remove()
     RNFetchBlob.cancelRequest(taskId, fn)
+    promiseReject(new Error("canceled"))
   }
   promise.taskId = taskId