insert env['SCRIPT_NAME'] before on_failure path

handle sub_uri (a.k.a. BaseURI) at on_failure

lib/omniauth.rb

@@ -24,7 +24,7 @@ module OmniAuth
       :path_prefix => '/auth',
       :on_failure => Proc.new do |env|
         message_key = env['omniauth.error.type']
-        new_path = "#{OmniAuth.config.path_prefix}/failure?message=#{message_key}"
+        new_path = "#{env['SCRIPT_NAME']}#{OmniAuth.config.path_prefix}/failure?message=#{message_key}"
         [302, {'Location' => new_path, 'Content-Type'=> 'text/html'}, []]
       end,
       :form_css => Form::DEFAULT_CSS,

spec/omniauth/strategy_spec.rb

@@ -496,6 +496,18 @@ describe OmniAuth::Strategy do
         response[1]['Location'].should == '/sub_uri/auth/test/callback'
       end
 
+      it 'should redirect on failure' do
+        response = OmniAuth.config.on_failure.call(make_env('/auth/test', 'omniauth.error.type' => 'error'))
+        response[0].should == 302
+        response[1]['Location'].should == '/auth/failure?message=error'
+      end
+
+      it 'should respect SCRIPT_NAME (a.k.a. BaseURI) on failure' do
+        response = OmniAuth.config.on_failure.call(make_env('/auth/test', 'SCRIPT_NAME' => '/sub_uri', 'omniauth.error.type' => 'error'))
+        response[0].should == 302
+        response[1]['Location'].should == '/sub_uri/auth/failure?message=error'
+      end
+
       it 'should be case insensitive on callback path' do
         strategy.call(make_env('/AUTH/TeSt/CaLlBAck')).should == strategy.call(make_env('/auth/test/callback'))
       end