bpo-45249: Add regression test for display of SyntaxError range indicator in doctests

Lib/test/test_doctest3.py

@@ -0,0 +1,16 @@
+import unittest
+import io
+import contextlib
+import doctest
+
+class TestDoctest(unittest.TestCase):
+    def test_syntax_error(self):
+        f = io.StringIO()
+        with contextlib.redirect_stdout(f):
+            doctest.run_docstring_examples('>>> 1 1', globals())
+        self.assertIn('''
+        1 1
+        ^^^
+    SyntaxError: invalid syntax. Perhaps you forgot a comma?''',
+        f.getvalue())
+

Misc/NEWS.d/next/Library/2021-09-26-09-56-46.bpo-45249.RG5p25.rst

@@ -0,0 +1,2 @@
+Added regression test for caret indicators of :exc:`SyntaxError` errors
+in :mod:`doctest`.