Selector should not receive both response and text

scrapy/selector/unified.py

@@ -46,6 +46,10 @@ class Selector(_ParselSelector, object_ref):
     selectorlist_cls = SelectorList
 
     def __init__(self, response=None, text=None, type=None, root=None, _root=None, **kwargs):
+        if not(response is None or text is None):
+           raise ValueError('%s.__init__() received both response and text'
+                            % self.__class__.__name__)
+
         st = _st(response, type or self._default_type)
 
         if _root is not None:

tests/test_selector.py

@@ -123,6 +123,10 @@ class SelectorTestCase(unittest.TestCase):
             sel.xpath('//p').extract_unquoted()
             self.assertSubstring('Use .extract() instead', str(w[-1].message))
 
+    def test_selector_bad_args(self):
+        with self.assertRaisesRegexp(ValueError, 'received both response and text'):
+            Selector(TextResponse(url='http://example.com', body=b''), text=u'')
+
 
 class DeprecatedXpathSelectorTest(unittest.TestCase):