common: fix UnicodeDecodeError in get_operations()

Closes #393

circle/common/operations.py

@@ -170,8 +170,8 @@ class Operation(object):
             raise ImproperlyConfigured(
                 "Set required_perms to () if none needed.")
         if not user.has_perms(cls.required_perms):
-            raise PermissionDenied("%s doesn't have the required permissions."
-                                   % user)
+            raise PermissionDenied(
+                u"%s doesn't have the required permissions." % user)
         if cls.superuser_required and not user.is_superuser:
             raise humanize_exception(ugettext_noop(
                 "Superuser privileges are required."), PermissionDenied())