Use a file context manager for test_ioctl.

Lib/test/test_ioctl.py

@@ -30,7 +30,7 @@ class IoctlTests(unittest.TestCase):
         # If this process has been put into the background, TIOCGPGRP returns
         # the session ID instead of the process group id.
         ids = (os.getpgrp(), os.getsid(0))
-        tty = open("/dev/tty", "r")
+        with open("/dev/tty", "r") as tty:
             r = fcntl.ioctl(tty, termios.TIOCGPGRP, "    ")
             rpgrp = struct.unpack("i", r)[0]
             self.assertIn(rpgrp, ids)