build: import StringIO on Python 2 and Python 3

This change supports access to StringIO on both Python 2 and Python 3

PR-URL: #1836
Reviewed-By: Rod Vagg <r@va.gg>
Reviewed-By: João Reis <reis@janeasystems.com>

gyp/pylib/gyp/MSVSSettings_test.py

@@ -6,15 +6,19 @@
 
 """Unit tests for the MSVSSettings.py file."""
 
-import StringIO
+try:
+  from cStringIO import StringIO
+except ImportError:
+  from io import StringIO
+
 import unittest
 import gyp.MSVSSettings as MSVSSettings
 
 
 class TestSequenceFunctions(unittest.TestCase):
 
   def setUp(self):
-    self.stderr = StringIO.StringIO()
+    self.stderr = StringIO()
 
   def _ExpectedWarnings(self, expected):
     """Compares recorded lines to expected warnings."""

gyp/pylib/gyp/easy_xml_test.py

@@ -8,13 +8,16 @@
 
 import gyp.easy_xml as easy_xml
 import unittest
-import StringIO
+try:
+  from cStringIO import StringIO
+except ImportError:
+  from io import StringIO
 
 
 class TestSequenceFunctions(unittest.TestCase):
 
   def setUp(self):
-    self.stderr = StringIO.StringIO()
+    self.stderr = StringIO()
 
   def test_EasyXml_simple(self):
     self.assertEqual(

gyp/pylib/gyp/generator/msvs_test.py

@@ -7,13 +7,16 @@
 
 import gyp.generator.msvs as msvs
 import unittest
-import StringIO
+try:
+  from cStringIO import StringIO
+except ImportError:
+  from io import StringIO
 
 
 class TestSequenceFunctions(unittest.TestCase):
 
   def setUp(self):
-    self.stderr = StringIO.StringIO()
+    self.stderr = StringIO()
 
   def test_GetLibraries(self):
     self.assertEqual(

gyp/pylib/gyp/generator/ninja.py

@@ -19,7 +19,10 @@
 import gyp.msvs_emulation
 import gyp.MSVSUtil as MSVSUtil
 import gyp.xcode_emulation
-from cStringIO import StringIO
+try:
+  from cStringIO import StringIO
+except ImportError:
+  from io import StringIO
 
 from gyp.common import GetEnvironFallback
 import gyp.ninja_syntax as ninja_syntax

gyp/pylib/gyp/generator/ninja_test.py

@@ -8,7 +8,6 @@
 
 import gyp.generator.ninja as ninja
 import unittest
-import StringIO
 import sys
 import TestCommon