[navigation][models] Move __unicode__ to __str__

__unicode__ is a leftover of Python 2

beat/web/navigation/models.py

@@ -29,19 +29,15 @@ from django.db import models
 from django.contrib.auth.models import User
 
 
-#----------------------------------------------------------
+# ----------------------------------------------------------
 
 
 class Agreement(models.Model):
 
     user = models.OneToOneField(User)
     version = models.PositiveIntegerField(
-        default=1,
-        help_text='Last version of the ToS the user has agreed with',
+        default=1, help_text="Last version of the ToS the user has agreed with"
     )
 
-    def __unicode__(self):
-        return u"%s agrees with ToS version %d" % (
-            self.user.username,
-            self.version
-        )
+    def __str__(self):
+        return "%s agrees with ToS version %d" % (self.user.username, self.version)