ReSizeStream: reminder type

1. Change ReSizeStream.reminder type to bytes according to stream data
   type.

2. Add test for ReSizeStream

3. Also update ReSizeStream.read to use self.__next__() instead of
   nonexistent self.next().
   Relates to change id I940841b94789d024d3b9447f96158963fe3e16ee where
   ReSizeStream.next() was renamed to ReSizeStream.__next__().

Story: 2010167
Task: 45860
Change-Id: I5eb70419d2ee795a18f67594e426b942e5390c7b

freezer/tests/commons.py

@@ -15,6 +15,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from io import BytesIO
 import os
 from unittest import mock
 
@@ -211,7 +212,7 @@ class FakeGlanceClient(object):
 
         @staticmethod
         def data(image):
-            return glance_utils.IterableWithLength(iter("abc"), 3)
+            return glance_utils.IterableWithLength(BytesIO(b"abc"), 3)
 
         @staticmethod
         def delete(image):

freezer/tests/unit/utils/test_utils.py

@@ -15,6 +15,7 @@
 
 import datetime
 import fixtures
+from io import BytesIO
 import os
 import time
 from unittest import mock
@@ -215,3 +216,30 @@ class TestDateTime(object):
         condition = mock.MagicMock(side_effect=[False, False, False])
         self.assertRaises(exception_utils.TimeoutException,
                           utils.wait_for(condition, 0.1, 0.2))
+
+
+class TestReSizeStream(commons.FreezerBaseTestCase):
+    def test_next(self):
+        stream_data = b"12345"
+        stream = BytesIO(stream_data)
+        chunk_size = len(stream_data) - 1
+        resize_stream = utils.ReSizeStream(
+            stream=stream,
+            length=len(stream_data),
+            chunk_size=chunk_size,
+        )
+        next_result = next(resize_stream)
+        self.assertEqual(chunk_size, len(next_result))
+        self.assertEqual(stream_data[:chunk_size], next_result)
+        self.assertIsInstance(next_result, bytes)
+
+    def test_read(self):
+        stream_data = b"abcdef"
+        chunk_size = 2
+        resize_stream = utils.ReSizeStream(
+            stream=BytesIO(stream_data),
+            length=len(stream_data),
+            chunk_size=chunk_size,
+        )
+        read_result = resize_stream.read(chunk_size)
+        self.assertEqual(stream_data[:chunk_size], read_result)

freezer/utils/utils.py

@@ -254,7 +254,7 @@ class ReSizeStream(object):
         self.stream = stream
         self.length = length
         self.chunk_size = chunk_size
-        self.reminder = ""
+        self.reminder = bytes()
         self.transmitted = 0
 
     def __len__(self):
@@ -287,7 +287,7 @@ class ReSizeStream(object):
                 result = self.reminder
                 if len(self.reminder) == 0:
                     raise StopIteration()
-                self.reminder = []
+                self.reminder = bytes()
                 self.transmitted += len(result)
                 return result
             else:
@@ -298,7 +298,7 @@ class ReSizeStream(object):
 
     def read(self, chunk_size):
         self.chunk_size = chunk_size
-        return self.next()
+        return self.__next__()
 
 
 def dequote(s):