Handle serverNotFound error

AppleLibs/Network/Requests/DataManager.swift

@@ -155,6 +155,8 @@ open class DataManager: NSObject, URLSessionDelegate
             return ResponseError.networkError(url: url, error: .noInternet)
         } else if error.code == NSURLErrorTimedOut {
             return ResponseError.networkError(url: url, error: .timeout)
+        } else if error.code == NSURLErrorCannotConnectToHost {
+            return ResponseError.networkError(url: url, error: .serverNotFound)
         }
         return ResponseError.networkError(url: url, error: .unknown(error: error))
     }