Error in app building

whenever I try to generate some application the error occurs:

(node: 320) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside an async function without a catch block, or by rejecting a promise which was not handled with .catch (). (rejection id: 1)
(node: 320) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

this happens even in a blank app

Those are warnings that should be non-fatal. If your app is not actually building, look for other messages.