I keep getting an error that my app needs to be verified when either I or another user try to authorize with OAuth2. What does that mean?

I received this error when trying to authorize my app with my own account:

Your project is trying to access scopes that need to go through the verification process.

{invalid=https://www.googleapis.com/auth/contacts}

If you need to use one of these scopes, submit a verification request. Learn More

When I use a different account, the error message is different:

This app hasn’t been verified to access:
{invalid=https://www.googleapis.com/auth/contacts}


Are you the developer? If this project needs these scopes, sign in to an account with access to edit your project and try again.

If not, contact the developer for help.