Use gettext_lazy for Python 3 code

src/robots/admin.py

@@ -1,8 +1,14 @@
+import sys
+
 from django.contrib import admin
-from django.utils.translation import ugettext_lazy as _
 from robots.forms import RuleAdminForm
 from robots.models import Rule, Url
 
+if sys.version_info[0] == 2:
+    from django.utils.translation import ugettext_lazy as _
+else:
+    from django.utils.translation import gettext_lazy as _
+
 
 class RuleAdmin(admin.ModelAdmin):
     form = RuleAdminForm

src/robots/forms.py

@@ -1,7 +1,13 @@
+import sys
+
 from django import forms
-from django.utils.translation import ugettext_lazy as _
 from robots.models import Rule
 
+if sys.version_info[0] == 2:
+    from django.utils.translation import ugettext_lazy as _
+else:
+    from django.utils.translation import gettext_lazy as _
+
 
 class RuleAdminForm(forms.ModelForm):
     class Meta:

src/robots/models.py

@@ -1,9 +1,15 @@
+import sys
+
 from django.contrib.sites.models import Site
 from django.db import models
 from django.utils.text import get_text_list
-from django.utils.translation import ugettext_lazy as _
 from six import python_2_unicode_compatible, u
 
+if sys.version_info[0] == 2:
+    from django.utils.translation import ugettext_lazy as _
+else:
+    from django.utils.translation import gettext_lazy as _
+
 
 @python_2_unicode_compatible
 class Url(models.Model):