tests: Restore stdout

Before this commit, test_run_default_format_output_in_tty() changed the
value of sys.stdout, but it would never change it back to the original
value. This commit makes sure that it gets changed back.

At the moment, this commit doesn’t make a user-visible difference. A
future commit will add a new test named
test_ignored_from_file_with_multiple_encodings(). That new test requires
that stdout gets restored, or else it will fail.

Author: Jayman2000

tests/test_cli.py

@@ -498,6 +498,7 @@ def test_run_default_format_output_in_tty(self):
         path = os.path.join(self.wd, 'a.yaml')
 
         # Create a pseudo-TTY and redirect stdout to it
+        old_stdout = sys.stdout
         master, slave = pty.openpty()
         sys.stdout = os.fdopen(slave, 'w')
 
@@ -515,6 +516,7 @@ def test_run_default_format_output_in_tty(self):
 
         sys.stdout.close()
         output.close()
+        sys.stdout = old_stdout
 
         self.assertEqual(out, (
             f'\033[4m{path}\033[0m\n'