Fix metaclass issue on Python 3. Get text handling tests passing on Python 3.

Signed-off-by: Dan O'Reilly <oreilldf@gmail.com>

python/google/protobuf/descriptor.py

@@ -36,6 +36,8 @@ file, in types that make this information accessible in Python.
 
 __author__ = 'robinson@google.com (Will Robinson)'
 
+import six
+
 from google.protobuf.internal import api_implementation
 
 
@@ -73,7 +75,7 @@ else:
   DescriptorMetaclass = type
 
 
-class DescriptorBase(object):
+class DescriptorBase(six.with_metaclass(DescriptorMetaclass)):
 
   """Descriptors base class.
 
@@ -88,7 +90,6 @@ class DescriptorBase(object):
         avoid some bootstrapping issues.
   """
 
-  __metaclass__ = DescriptorMetaclass
   if _USE_C_DESCRIPTORS:
     # The class, or tuple of classes, that are considered as "virtual
     # subclasses" of this descriptor class.

python/google/protobuf/text_format.py

@@ -69,19 +69,15 @@ class ParseError(Error):
 
 class TextWriter(object):
   def __init__(self, as_utf8):
-    self._utf8 = as_utf8
-    if as_utf8:
+    if six.PY2:
       self._writer = io.BytesIO()
     else:
       self._writer = io.StringIO()
 
   def write(self, val):
-    if self._utf8:
+    if six.PY2:
       if isinstance(val, six.text_type):
         val = val.encode('utf-8')
-    else:
-      if isinstance(val, bytes):
-        val = val.decode('utf-8')
     return self._writer.write(val)
 
   def close(self):
@@ -245,8 +241,7 @@ def PrintFieldValue(field, value, out, indent=0, as_utf8=False,
       out_as_utf8 = False
     else:
       out_as_utf8 = as_utf8
-    out_text = text_encoding.CEscape(out_value, out_as_utf8)
-    out.write(out_text)
+    out.write(text_encoding.CEscape(out_value, out_as_utf8))
     out.write('\"')
   elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_BOOL:
     if value:

python/tox.ini

@@ -1,9 +1,9 @@
 [tox]
 envlist =
-    # Py3 tests currently fail because of text handling issues,
-    # So only test py26/py27 for now.
+    # cpp implementation on py34 is currently broken due to
+    # changes introduced by http://bugs.python.org/issue22079.
     #py{26,27,33,34}-{cpp,python}
-    py{26,27}-{cpp,python}
+    py{26,27,33}-{cpp,python}, py34-{python}
 
 [testenv]
 usedevelop=true