[UserProjectIntegrator] Warn about xcconfig override after every installation /2

lib/cocoapods/installer/user_project_integrator.rb

@@ -144,7 +144,7 @@ module Pod
             user_target.build_configurations.each do |config|
               xcconfig = aggregate_target.xcconfigs[config.name]
               if xcconfig
-                xcconfig.attributes.keys.each do |key|
+                xcconfig.to_hash.keys.each do |key|
                   target_value = config.build_settings[key]
                   if target_value && !target_value.include?('$(inherited)')
                     print_override_warning(aggregate_target, user_target, config, key)

spec/unit/installer/user_project_integrator_spec.rb

@@ -61,7 +61,7 @@ module Pod
           user_target = stub(:name => 'SampleProject', :build_configurations => [target_config])
           @library.stubs(:user_targets).returns([user_target])
 
-          @library.xcconfigs['Release'] = stub(:attributes => {'GCC_PREPROCESSOR_DEFINITIONS' => 'COCOAPODS=1'})
+          @library.xcconfigs['Release'] = {'GCC_PREPROCESSOR_DEFINITIONS' => 'COCOAPODS=1'}
           @integrator = UserProjectIntegrator.new(@podfile, config.sandbox, temporary_directory, [@library])
 
           @integrator.unstub(:warn_about_xcconfig_overrides)
@@ -76,7 +76,7 @@ module Pod
           user_target = stub(:name => 'SampleProject', :build_configurations => [target_config])
           @library.stubs(:user_targets).returns([user_target])
 
-          @library.xcconfigs['Release'] = stub(:attributes => {'GCC_PREPROCESSOR_DEFINITIONS' => 'COCOAPODS=1'})
+          @library.xcconfigs['Release'] = {'GCC_PREPROCESSOR_DEFINITIONS' => 'COCOAPODS=1'}
           @integrator = UserProjectIntegrator.new(@podfile, config.sandbox, temporary_directory, [@library])
 
           @integrator.unstub(:warn_about_xcconfig_overrides)