Fix test_cmd_line.test_non_interactive_output_buffering fail with PYTHONUNBUFFERED=1

Author: WolframAlph

Lib/test/test_cmd_line.py

@@ -337,6 +337,9 @@ def test_osx_android_utf8(self):
         self.assertEqual(p.returncode, 0)
 
     def test_non_interactive_output_buffering(self):
+        PYTHONUNBUFFERED_ENV_VAR = os.environ["PYTHONUNBUFFERED"]
+        # we expect buffered stdio
+        os.environ["PYTHONUNBUFFERED"] = "0"
         code = textwrap.dedent("""
             import sys
             out = sys.stdout
@@ -350,6 +353,8 @@ def test_non_interactive_output_buffering(self):
         self.assertEqual(proc.stdout,
                          'False False False\n'
                          'False False True\n')
+        # restore original value
+        os.environ["PYTHONUNBUFFERED"] = PYTHONUNBUFFERED_ENV_VAR
 
     def test_unbuffered_output(self):
         # Test expected operation of the '-u' switch