Removed remaining dependence on six for Python.

python/google/protobuf/internal/_parameterized.py

@@ -154,8 +154,6 @@ except ImportError:
   import unittest
 import uuid
 
-import six
-
 try:
   # Since python 3
   import collections.abc as collections_abc
@@ -181,7 +179,7 @@ def _StrClass(cls):
 
 def _NonStringIterable(obj):
   return (isinstance(obj, collections_abc.Iterable) and not
-          isinstance(obj, six.string_types))
+          isinstance(obj, str))
 
 
 def _FormatParameterList(testcase_params):

python/google/protobuf/internal/well_known_types.py

@@ -43,7 +43,6 @@ __author__ = 'jieluo@google.com (Jie Luo)'
 import calendar
 from datetime import datetime
 from datetime import timedelta
-import six
 
 try:
   # Since python 3
@@ -143,7 +142,7 @@ class Timestamp(object):
     Raises:
       ValueError: On parsing problems.
     """
-    if not isinstance(value, six.string_types):
+    if not isinstance(value, str):
       raise ValueError('Timestamp JSON value not a string: {!r}'.format(value))
     timezone_offset = value.find('Z')
     if timezone_offset == -1:
@@ -305,7 +304,7 @@ class Duration(object):
     Raises:
       ValueError: On parsing problems.
     """
-    if not isinstance(value, six.string_types):
+    if not isinstance(value, str):
       raise ValueError('Duration JSON value not a string: {!r}'.format(value))
     if len(value) < 1 or value[-1] != 's':
       raise ValueError(
@@ -432,7 +431,7 @@ class FieldMask(object):
 
   def FromJsonString(self, value):
     """Converts string to FieldMask according to proto3 JSON spec."""
-    if not isinstance(value, six.string_types):
+    if not isinstance(value, str):
       raise ValueError('FieldMask JSON value not a string: {!r}'.format(value))
     self.Clear()
     if value:
@@ -718,9 +717,6 @@ def _AddFieldPaths(node, prefix, field_mask):
     _AddFieldPaths(node[name], child_path, field_mask)
 
 
-_INT_OR_FLOAT = six.integer_types + (float,)
-
-
 def _SetStructValue(struct_value, value):
   if value is None:
     struct_value.null_value = 0
@@ -728,9 +724,9 @@ def _SetStructValue(struct_value, value):
     # Note: this check must come before the number check because in Python
     # True and False are also considered numbers.
     struct_value.bool_value = value
-  elif isinstance(value, six.string_types):
+  elif isinstance(value, str):
     struct_value.string_value = value
-  elif isinstance(value, _INT_OR_FLOAT):
+  elif isinstance(value, (int, float)):
     struct_value.number_value = value
   elif isinstance(value, (dict, Struct)):
     struct_value.struct_value.Clear()