Return Oauth headers even if none scope was matched

If an endpoint specifies more than one scope and none of the scopes from
access token matches, return oauth headers for the first of the scopes

lib/travis/api/app/extensions/scoping.rb

@@ -46,6 +46,9 @@ class Travis::Api::App
           end
 
           if !result
+            headers['X-OAuth-Scopes'] = scopes.map(&:to_s).join(',')
+            headers['X-Accepted-OAuth-Scopes'] = names.first.to_s
+
             if env['travis.access_token']
               pass { halt 403, "insufficient access" }
             else