From a96385dc315563abdd08e5a43b196a370209f984 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Schw=C3=A4rzl?= <thomas.schwaerzl@gmail.com>
Date: Thu, 25 Apr 2019 11:48:07 +0200
Subject: [PATCH] :bug: check if the username begins or ends with a period

---
 openbook_auth/validators.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/openbook_auth/validators.py b/openbook_auth/validators.py
index 2c0a40d1..fa4d9995 100644
--- a/openbook_auth/validators.py
+++ b/openbook_auth/validators.py
@@ -6,9 +6,9 @@
 
 
 def username_characters_validator(username):
-    if not re.match('^[a-zA-Z0-9_.]*$', username):
+    if not re.match('^(?!\.)[a-zA-Z0-9_.]*(?<!\.)$', username):
         raise ValidationError(
-            _('Usernames can only contain alphanumeric characters, periods and underscores.'),
+            _('Usernames can only contain alphanumeric characters, periods and underscores. They must not begin or end with a period.'),
         )