Fix test: override __repr__()

Author: vstinner

Doc/c-api/unicode.rst

@@ -574,7 +574,7 @@ APIs:
 
       * - ``#R``
         - :c:expr:`PyObject*`
-        - Similar to ``R`` format, but don't call :meth:`~object.__str__`
+        - Similar to ``R`` format, but don't call :meth:`~object.__repr__`
           method on :class:`str` subclasses.
 
       * - ``T``

Lib/test/test_capi/test_unicode.py

@@ -460,11 +460,11 @@ def check_format(expected, format, *args):
         check_format("'abc'",
                      b'%#R', 'abc')
         class StrSubclass(str):
-            def __str__(self):
+            def __repr__(self):
                 return 'StrSubclass'
         check_format("'abc'",
                      b'%#R', StrSubclass('abc'))
-        self.assertEqual(str(StrSubclass()), 'StrSubclass')
+        self.assertEqual(repr(StrSubclass()), 'StrSubclass')
 
         check_format('\u20acAB',
                      b'%.3V', '\u20acABCDEF', None)