Issue python#29145: Merge test from 3.6

Author: vadmium

Lib/test/test_unicode.py

@@ -465,6 +465,13 @@ def __str__(self): return self.sval
         self.checkraises(TypeError, ' ', 'join', [1, 2, 3])
         self.checkraises(TypeError, ' ', 'join', ['1', '2', 3])
 
+    @unittest.skipIf(sys.maxsize > 2**32,
+        'needs too much memory on a 64-bit platform')
+    def test_join_overflow(self):
+        size = int(sys.maxsize**0.5) + 1
+        seq = ('A' * size,) * size
+        self.assertRaises(OverflowError, ''.join, seq)
+
     def test_replace(self):
         string_tests.CommonTest.test_replace(self)