bpo-31479: Always reset the signal alarm in tests (#3588)

* bpo-31479: Always reset the signal alarm in tests

Use "try: ... finally: signal.signal(0)" pattern to make sure that
tests don't "leak" a pending fatal signal alarm.

* Move two more alarm() calls into the try block

Fix also typo: replace signal.signal(0) with signal.alarm(0)

* Move another signal.alarm() into the try block

1 files changed, 3 insertions, 0 deletions

diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index d4685dd..ce4ed1b8 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -3940,6 +3940,7 @@ class SignalsTest(unittest.TestCase):
             if isinstance(exc, RuntimeError):
                 self.assertTrue(str(exc).startswith("reentrant call"), str(exc))
         finally:
+            signal.alarm(0)
             wio.close()
             os.close(r)
 
@@ -3968,6 +3969,7 @@ class SignalsTest(unittest.TestCase):
             # - third raw read() returns b"bar"
             self.assertEqual(decode(rio.read(6)), "foobar")
         finally:
+            signal.alarm(0)
             rio.close()
             os.close(w)
             os.close(r)
@@ -4035,6 +4037,7 @@ class SignalsTest(unittest.TestCase):
             self.assertIsNone(error)
             self.assertEqual(N, sum(len(x) for x in read_results))
         finally:
+            signal.alarm(0)
             write_finished = True
             os.close(w)
             os.close(r)