Use universal newlines for running Google test

Author: elkin

pytest_cpp/google.py

@@ -61,7 +61,9 @@ def run_test(self, executable, test_id):
             '--gtest_output=xml:%s' % xml_filename,
         ]
         try:
-            subprocess.check_output(args, stderr=subprocess.STDOUT)
+            subprocess.check_output(args,
+                                    stderr=subprocess.STDOUT,
+                                    universal_newlines=True)
         except subprocess.CalledProcessError as e:
             if e.returncode != 1:
                 msg = ('Internal Error: calling {executable} '