From de872282b264b51db2ca10fb9e61f5815bd66b4d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9gis=20Behmo?= <regis@behmo.com>
Date: Thu, 25 Feb 2021 09:54:46 +0100
Subject: [PATCH] fix: minor edge case in `long_to_base64` utility function.

This was detected by mypy.
---
 CHANGELOG.md        | 2 ++
 tests/test_utils.py | 4 ++++
 tutor/utils.py      | 2 +-
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fd366f1..9a9f582 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@ Note: Breaking changes between versions are indicated by "💥".
 
 ## Unreleased
 
+- [Bugfix] Fix minor edge case in `long_to_base64` utility function.
+
 ## v11.2.3 (2021-02-20)
 
 - [Bugfix] Make LMS celery workers actually process LMS tasks, and not CMS tasks.
diff --git a/tests/test_utils.py b/tests/test_utils.py
index c056b3d..1770ae5 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -1,3 +1,4 @@
+import base64
 import unittest
 
 from tutor import utils
@@ -30,3 +31,6 @@ class UtilsTests(unittest.TestCase):
         self.assertNotEqual(encrypted1, encrypted2)
         self.assertTrue(utils.verify_encrypted(encrypted1, password))
         self.assertTrue(utils.verify_encrypted(encrypted2, password))
+
+    def test_long_to_base64(self):
+        self.assertEqual(b"\x00", base64.urlsafe_b64decode(utils.long_to_base64(0) + "=="))
diff --git a/tutor/utils.py b/tutor/utils.py
index f7b859f..9705f01 100644
--- a/tutor/utils.py
+++ b/tutor/utils.py
@@ -112,7 +112,7 @@ def long_to_base64(n):
     bys = long2intarr(n)
     data = struct.pack("%sB" % len(bys), *bys)
     if not data:
-        data = "\x00"
+        data = b"\x00"
     s = base64.urlsafe_b64encode(data).rstrip(b"=")
     return s.decode("ascii")