Ominiauth facebook with rails application

I have used ominiauth for login with facebook in my rails application. My problem is handling errors and displaying proper message. As an example when the site url is not correct I get below content in the browser.

{ "error": { "message": "Invalid redirect_uri: Given URL is not permitted by the Application configuration", "type": "OAuthException", "code": 191 } }

What I want is to get the message and display as a flash message in same page where I call facebook login. How can I achieve this? Please help