Make swift and obj-c patterns Python3 compatible (dropbox#203)

* Make swift and obj-c patterns Python3 compatible
* Remove trailing whitespace
* Bump six version

requirements.txt

@@ -0,0 +1,2 @@
+ply>= 3.4
+six>= 1.12.0

stone/backends/obj_c_types.py

@@ -3,6 +3,7 @@
 import json
 import os
 import shutil
+import six
 
 from stone.ir import (
     is_list_type,
@@ -911,7 +912,8 @@ def _determine_validator_type(self, data_type, value, has_default):
         elif is_string_type(data_type):
             if data_type.pattern or data_type.min_length or data_type.max_length:
                 pattern = data_type.pattern.encode('unicode_escape').replace(
-                    "\"", "\\\"") if data_type.pattern else None
+                    six.ensure_binary("\""),
+                    six.ensure_binary("\\\"")) if data_type.pattern else None
                 validator = '{}:{}'.format(
                     fmt_validator(data_type),
                     fmt_func_args([

stone/backends/swift_types.py

@@ -3,6 +3,7 @@
 import json
 import os
 import shutil
+import six
 
 from contextlib import contextmanager
 
@@ -235,7 +236,8 @@ def _determine_validator_type(self, data_type, value):
             )
         elif is_string_type(data_type):
             pat = data_type.pattern if data_type.pattern else None
-            pat = pat.encode('unicode_escape').replace("\"", "\\\"") if pat else pat
+            pat = pat.encode('unicode_escape').replace(six.ensure_binary("\""),
+                                                       six.ensure_binary("\\\"")) if pat else pat
             v = "stringValidator({})".format(
                 self._func_args([
                     ("minLength", data_type.min_length),