make property deletions evaluate to false for convenience

owrx/property/__init__.py

@@ -11,7 +11,8 @@ class PropertyError(Exception):
 
 
 class PropertyDeletion(object):
-    pass
+    def __bool__(self):
+        return False
 
 
 # a special object that will be sent in events when a deletion occured

test/property/test_property_deletion.py

@@ -0,0 +1,8 @@
+from unittest import TestCase
+from owrx.property import PropertyDeletion
+
+
+class PropertyDeletionTest(TestCase):
+    def testDeletionEvaluatesToFalse(self):
+        deletion = PropertyDeletion()
+        self.assertFalse(deletion)