fix: django.utils.six not available before django 1.6

jsignature/fields.py

@@ -4,16 +4,16 @@
 """
 import json
 import six
+
 from django.db import models
 from django.core.exceptions import ValidationError
-from django.utils.six import with_metaclass
 
 from .forms import (
     JSignatureField as JSignatureFormField,
     JSIGNATURE_EMPTY_VALUES)
 
 
-class JSignatureField(with_metaclass(models.SubfieldBase, models.Field)):
+class JSignatureField(six.with_metaclass(models.SubfieldBase, models.Field)):
     """
     A model field handling a signature captured with jSignature
     """

jsignature/tests/fields.py

@@ -1,5 +1,6 @@
 import json
 import six
+
 from django.test import SimpleTestCase
 from django.core.exceptions import ValidationError
 

jsignature/widgets.py

@@ -9,6 +9,7 @@ from django.template.loader import render_to_string
 from django.forms.widgets import HiddenInput
 from django.core import validators
 from django.core.exceptions import ValidationError
+
 from django.utils.safestring import mark_safe
 from django.utils.translation import ugettext_lazy as _
 from jsignature.settings import JSIGNATURE_DEFAULT_CONFIG