Merge Replace sigalarm-based subprocess timeout with the built-in one

The timeout parameter for subprocess.Popen.communicate has been available since Python 3.3. Given the fragility of SIGALRM based mechanisms, there's no reason to reimplement our own timeout instead of using the built-in one.

MR: https://gitlab.com/apparmor/apparmor/-/merge_requests/1377
Approved-by: Christian Boltz <apparmor@cboltz.de>
Merged-by: Christian Boltz <apparmor@cboltz.de>

parser/tst/testlib.py

@@ -98,12 +98,11 @@ class AATestTemplate(unittest.TestCase, metaclass=AANoCleanupMetaClass):
         except OSError as e:
             return 127, str(e), ''
 
-        timeout_communicate = TimeoutFunction(sp.communicate, timeout)
         out, outerr = (None, None)
         try:
-            out, outerr = timeout_communicate(input)
+            out, outerr = sp.communicate(input, timeout)
             rc = sp.returncode
-        except TimeoutFunctionException:
+        except subprocess.TimeoutExpired:
             sp.terminate()
             outerr = 'test timed out, killed'
             rc = TIMEOUT_ERROR_CODE
@@ -117,31 +116,6 @@ class AATestTemplate(unittest.TestCase, metaclass=AANoCleanupMetaClass):
 
         return rc, out, outerr
 
-
-# Timeout handler using alarm() from John P. Speno's Pythonic Avocado
-class TimeoutFunctionException(Exception):
-    """Exception to raise on a timeout"""
-
-
-class TimeoutFunction:
-    def __init__(self, function, timeout):
-        self.timeout = timeout
-        self.function = function
-
-    def handle_timeout(self, signum, frame):
-        raise TimeoutFunctionException()
-
-    def __call__(self, *args, **kwargs):
-        old = signal.signal(signal.SIGALRM, self.handle_timeout)
-        signal.alarm(self.timeout)
-        try:
-            result = self.function(*args, **kwargs)
-        finally:
-            signal.signal(signal.SIGALRM, old)
-        signal.alarm(0)
-        return result
-
-
 def filesystem_time_resolution():
     """detect whether the filesystem stores subsecond timestamps"""