do not use ElementTree.__nonzero__; add test for mixed content (twilio#429)

ekarson · web-flow · commit 6f7e2afa71e0 · 2018-06-21T08:30:22.000-07:00
diff --git a/tests/unit/twiml/test_messaging_response.py b/tests/unit/twiml/test_messaging_response.py
@@ -51,6 +51,18 @@ def test_child_node(self):
             self.strip(r),
             '<?xml version="1.0" encoding="UTF-8"?><Response><message tag="global"><bold>Hello</bold></message></Response>')
 
+    def test_mixed(self):
+        r = MessagingResponse()
+
+        r.append('before')
+        r.add_child('Child').append('content')
+        r.append('after')
+
+        assert_equal(
+            self.strip(r),
+            '<?xml version="1.0" encoding="UTF-8"?><Response>before<Child>content</Child>after</Response>'
+        )
+
 
 class TestMessage(TwilioTest):
 
diff --git a/twilio/twiml/__init__.py b/twilio/twiml/__init__.py
@@ -111,7 +111,7 @@ def xml(self):
 
         for verb in self.verbs:
             if isinstance(verb, str):
-                if last_child:
+                if last_child is not None:
                     last_child.tail = verb
                 else:
                     el.text = verb
