support/testing/tests/package/test_python_waitress: rework assertion

Like Yann E. Morin did for
support/testing/tests/package/test_python_django.py, adjust the logic
to avoid the weird "self.assertTrue(False, ...)" construct, and
instead test exit_code after the loop.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

support/testing/tests/package/test_python_waitress.py

@@ -30,5 +30,4 @@ class TestPythonWaitress(TestPythonPackageBase):
             if exit_code == 0:
                 self.assertEqual(output[0], 'Hello, World!')
                 break
-        else:
-            self.assertTrue(False, "Timeout while waiting for waitress server")
+        self.assertEqual(exit_code, 0, "Timeout while waiting for django server")