generate Twisted code in a separate directory (gen-py.twisted)

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@816340 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/compiler/cpp/src/generate/t_py_generator.cc b/compiler/cpp/src/generate/t_py_generator.cc
index e79e954..ec4095b 100644
--- a/compiler/cpp/src/generate/t_py_generator.cc
+++ b/compiler/cpp/src/generate/t_py_generator.cc
@@ -52,7 +52,11 @@
     iter = parsed_options.find("twisted");
     gen_twisted_ = (iter != parsed_options.end());
 
-    out_dir_base_ = "gen-py";
+    if (gen_twisted_){
+      out_dir_base_ = "gen-py.twisted";
+    } else {
+      out_dir_base_ = "gen-py";
+    }
   }
 
   /**