Downloading image with --progress fails

Downloading image with --progress fails with "RequestIdProxy object is
not an iterator". This is because to display download progress
VerboseFileWrapper in progressbar requires object of IterableWithLength,
but after support of returning request-id [1] to caller it returns
RequestIdProxy object which is wrapped around IterableWithLength
and response.

To resolve this issue overridden next and __next__ methods in
RequestIdProxy so that it can act as iterator for python 2.x
and 3.x as well.

[1] 610177a779

Closes-Bug: #1670464
Change-Id: I188e67c2487b7e4178ea246f02154bbcbc35a2b1

glanceclient/common/utils.py

@@ -494,6 +494,13 @@ class RequestIdProxy(wrapt.ObjectProxy):
     def wrapped(self):
         return self._self_wrapped
 
+    # Overriden next method to act as iterator
+    def next(self):
+        return next(self._self_wrapped)
+
+    # In Python 3, __next__() has replaced next().
+    __next__ = next
+
 
 class GeneratorProxy(wrapt.ObjectProxy):
     def __init__(self, wrapped):

glanceclient/tests/unit/test_progressbar.py

@@ -15,6 +15,7 @@
 
 import sys
 
+import requests
 import six
 import testtools
 
@@ -27,12 +28,16 @@ class TestProgressBarWrapper(testtools.TestCase):
 
     def test_iter_iterator_display_progress_bar(self):
         size = 100
+        # create fake response object to return request-id with iterator
+        resp = requests.Response()
+        resp.headers['x-openstack-request-id'] = 'req-1234'
         iterator_with_len = utils.IterableWithLength(iter('X' * 100), size)
+        requestid_proxy = utils.RequestIdProxy((iterator_with_len, resp))
         saved_stdout = sys.stdout
         try:
             sys.stdout = output = test_utils.FakeTTYStdout()
             # Consume iterator.
-            data = list(progressbar.VerboseIteratorWrapper(iterator_with_len,
+            data = list(progressbar.VerboseIteratorWrapper(requestid_proxy,
                                                            size))
             self.assertEqual(['X'] * 100, data)
             self.assertEqual(