merge 2.6.0 to trunk
diff --git a/python/README.txt b/python/README.txt
index 9ba42f8..adfa46b 100644
--- a/python/README.txt
+++ b/python/README.txt
@@ -48,8 +48,8 @@
      $ python setup.py build
      $ python setup.py google_test
 
-     if you want to test c++ implementation, run:
-     $ python setup.py test
+     If you want to test c++ implementation, run:
+     $ python setup.py test --cpp_implementation
 
    If some tests fail, this library may not work correctly on your
    system.  Continue at your own risk.
@@ -66,7 +66,7 @@
 
      $ python setup.py install
      or:
-     $ python setup.py install --nocpp_implementation
+     $ python setup.py install --cpp_implementation
 
    This step may require superuser privileges.
    NOTE: To use C++ implementation, you need to install C++ protobuf runtime
@@ -84,8 +84,6 @@
 C++ Implementation
 ==================
 
-WARNING: This is EXPERIMENTAL and only available for CPython platforms.
-
 The C++ implementation for Python messages is built as a Python extension to
 improve the overall protobuf Python performance.
 
diff --git a/python/setup.py b/python/setup.py
index 6eecd48..9441d0e 100755
--- a/python/setup.py
+++ b/python/setup.py
@@ -138,10 +138,9 @@
 
 if __name__ == '__main__':
   ext_module_list = []
-  nocpp = '--nocpp_implementation'
-  if nocpp in sys.argv:
+  cpp_impl = '--cpp_implementation'
+  if cpp_impl in sys.argv:
     sys.argv.remove(cpp_impl)
-  else:
     # C++ implementation extension
     ext_module_list.append(Extension(
         "google.protobuf.pyext._message",