fix empty body getter bug 1067923

Change-Id: Ifd609f305ee878c39ea4e6840ed8fa9369595cfa

swift/common/swob.py

@@ -300,6 +300,8 @@ def _resp_body_property():
     """
     def getter(self):
         if not self._body:
+            if not self._app_iter:
+                return ''
             self._body = ''.join(self._app_iter)
             self._app_iter = None
         return self._body

test/unit/common/test_swob.py

@@ -352,6 +352,11 @@ class TestResponse(unittest.TestCase):
         resp.content_type = None
         self.assert_('Content-Type' not in resp.headers)
 
+    def test_empty_body(self):
+        resp = self._get_response()
+        resp.body = ''
+        self.assertEquals(resp.body, '')
+
     def test_unicode_body(self):
         resp = self._get_response()
         resp.body = u'\N{SNOWMAN}'