Added tests for AssertionErrors in get_complete_version() and _lazy_re_compile().

tests/utils_tests/test_regex_helper.py

@@ -1,5 +1,7 @@
+import re
 import unittest
 
+from django.test import SimpleTestCase
 from django.utils import regex_helper
 
 
@@ -41,3 +43,12 @@ class NormalizeTests(unittest.TestCase):
                     ['first_group_name'])]
         result = regex_helper.normalize(pattern)
         self.assertEqual(result, expected)
+
+
+class LazyReCompileTests(SimpleTestCase):
+    def test_flags_with_pre_compiled_regex(self):
+        test_pattern = re.compile('test')
+        lazy_test_pattern = regex_helper._lazy_re_compile(test_pattern, re.I)
+        msg = 'flags must be empty if regex is passed pre-compiled'
+        with self.assertRaisesMessage(AssertionError, msg):
+            lazy_test_pattern.match('TEST')