Attempt to better handle python(2|3) tempfile differences

generate-flag-types

@@ -68,6 +68,9 @@ import tempfile
 import textwrap
 
 
+_PY3 = sys.version_info.major == 3
+
+
 class _FancyFormatter(argparse.ArgumentDefaultsHelpFormatter,
                       argparse.RawDescriptionHelpFormatter):
     pass
@@ -104,9 +107,7 @@ def main(sysargs=sys.argv[:]):
 def _generate_flag_types(writefunc, output_go, input_json):
     types = json.load(input_json)
 
-    tmp = tempfile.NamedTemporaryFile(
-        suffix='.go', mode='w', delete=False, encoding='utf-8'
-    )
+    tmp = _get_named_tmp_go()
     writefunc(tmp, types)
     tmp.close()
 
@@ -119,6 +120,13 @@ def _generate_flag_types(writefunc, output_go, input_json):
     os.remove(tmp.name)
 
 
+def _get_named_tmp_go():
+    tmp_args = dict(suffix='.go', mode='w', delete=False)
+    if _PY3:
+        tmp_args['encoding'] = 'utf-8'
+    return tempfile.NamedTemporaryFile(**tmp_args)
+
+
 def _set_typedef_defaults(typedef):
     typedef.setdefault('doctail', '')
     typedef.setdefault('context_type', typedef['type'])