Fixed handling http redirects

Override method 'redirect_request' for patching
new request, that has been created on handling
http redirect.

Closes-Bug: 1592464
Change-Id: Id32bc46cce2c0eabb91f645d01378b6da3128469

packetary/library/connections.py

@@ -93,9 +93,23 @@ class ResumableResponse(StreamWrapper):
                 self.stream = response.stream
 
 
-class RetryHandler(urllib.BaseHandler):
+class RetryHandler(urllib.HTTPRedirectHandler):
     """urllib Handler to add ability for retrying on server errors."""
 
+    def redirect_request(self, req, fp, code, msg, headers, newurl):
+        new_req = urllib.HTTPRedirectHandler.redirect_request(
+            self, req, fp, code, msg, headers, newurl
+        )
+        if new_req is not None:
+            # We use class assignment for casting new request to type
+            # RetryableRequest
+            new_req.__class__ = RetryableRequest
+            new_req.retries_left = req.retries_left
+            new_req.offset = req.offset
+            new_req.start_time = req.start_time
+            new_req.retry_interval = req.retry_interval
+        return new_req
+
     @staticmethod
     def http_request(request):
         """Initialises http request.
@@ -118,6 +132,11 @@ class RetryHandler(urllib.BaseHandler):
         :return: ResumableResponse if success otherwise same response
         """
         code, msg = response.getcode(), response.msg
+
+        if 300 <= code < 400:
+            # the redirect group, pass to next handler as is
+            return response
+
         # the server should response partial content if range is specified
         if request.offset > 0 and code != http_client.PARTIAL_CONTENT:
             raise RangeError(msg)

packetary/tests/test_connections.py

@@ -268,6 +268,25 @@ class TestRetryHandler(base.TestCase):
         self.handler.http_response(request, response_mock)
         self.handler.parent.open.assert_called_once_with(request)
 
+    @mock.patch(
+        'packetary.library.connections.urllib.'
+        'HTTPRedirectHandler.redirect_request'
+    )
+    def test_redirect_request(self, redirect_mock, _):
+        redirect_mock.return_value = connections.urllib.Request(
+            'http://localhost/'
+        )
+        req = mock.MagicMock(retries_left=10, retry_interval=5, offset=100)
+        new_req = self.handler.redirect_request(req, -1, 301, "", {}, "")
+        self.assertIsInstance(new_req, connections.RetryableRequest)
+        self.assertEqual(req.retries_left, new_req.retries_left)
+        self.assertEqual(req.retry_interval, new_req.retry_interval)
+        self.assertEqual(req.offset, new_req.offset)
+        redirect_mock.return_value = None
+        self.assertIsNone(
+            self.handler.redirect_request(req, -1, 301, "", {}, "")
+        )
+
 
 class TestResumeableResponse(base.TestCase):
     def setUp(self):