check that no extra kwargs are silently discarded

scrapy/core/downloader/handlers/s3.py

@@ -68,6 +68,9 @@ class S3DownloadHandler(object):
             except Exception as ex:
                 raise NotConfigured(str(ex))
         else:
+            kw.pop('anon', None)
+            if kw:
+                raise TypeError('Unexpected keyword arguments: %s' % kw)
             if not self.anon:
                 SignerCls = botocore.auth.AUTH_TYPE_MAPS['s3']
                 self._signer = SignerCls(botocore.credentials.Credentials(

tests/test_downloader_handlers.py

@@ -500,6 +500,10 @@ class S3TestCase(BaseS3TestCase):
                 mock_formatdate.return_value = date
                 yield
 
+    def test_extra_kw(self):
+        with self.assertRaises(TypeError):
+            S3DownloadHandler(Settings(), extra_kw=True)
+
     def test_request_signing1(self):
         # gets an object from the johnsmith bucket.
         date ='Tue, 27 Mar 2007 19:36:42 +0000'