Tweak filelock tests for Windows

In the tests where we "fake" someone else holding the lock by
just creating the lockfile, close the phony lockfile after
the test so Windows dowsn't get file access errors.

Signed-off-by: Mats Wichmann <mats@linux.com>

Author: mwichmann

SCons/Util/filelockTests.py

@@ -52,9 +52,9 @@ def tearDown(self):
         with suppress(FileNotFoundError):
             os.unlink(self.lockfile)
 
-    def _fakelock(self):
+    def _fakelock(self) -> int:
         """Create a fake lockfile to simulate a busy lock."""
-        _ = os.open(self.lockfile, os.O_CREAT|os.O_EXCL|os.O_RDWR)
+        return os.open(self.lockfile, os.O_CREAT|os.O_EXCL|os.O_RDWR)
 
     def test_context_manager_lock(self):
         """Test acquiring a file lock, context manager."""
@@ -81,16 +81,18 @@ def test_acquire_release_lock(self):
     def test_nonblocking_lockfail(self):
         """Test non-blocking acquiring a busy file lock."""
         self.lock = filelock.FileLock(self.file, writer=True)
-        self._fakelock()
+        fd = self._fakelock()
         with self.lock and self.assertRaises(filelock.AlreadyLockedError):
             self.lock.acquire_lock()
+        os.close(fd)
 
     def test_timeout_lockfail(self):
         """Test blocking acquiring a busy file lock with timeout."""
         self.lock = filelock.FileLock(self.file, writer=True, timeout=1)
-        self._fakelock()
+        fd = self._fakelock()
         with self.lock and self.assertRaises(filelock.LockTimeoutError):
             self.lock.acquire_lock()
+        os.close(fd)
 
 if __name__ == "__main__":
     unittest.main()