py3: Fix encoding and use sys.stdin.buffer

* exc.py: Encode body in response before calling replace over it.
* http.py: prepend the bytes literal to the empty string or else
  we hit bug 1342080 again in python 3.
* utils.py: Use sys.stdin.buffer in python 3.

Change-Id: Ieefb8c633658e507486438e5518c5d53e819027d

glanceclient/tests/unit/test_http.py

@@ -239,6 +239,14 @@ class TestClient(testtools.TestCase):
         test_client = http.HTTPClient(endpoint, token=u'adc123')
         self.assertEqual(600.0, test_client.timeout)
 
+    def test__chunk_body_exact_size_chunk(self):
+        test_client = http._BaseHTTPClient()
+        bytestring = b'x' * http.CHUNKSIZE
+        data = six.BytesIO(bytestring)
+        chunk = list(test_client._chunk_body(data))
+        self.assertEqual(1, len(chunk))
+        self.assertEqual([bytestring], chunk)
+
     def test_http_chunked_request(self):
         text = "Ok"
         data = six.StringIO(text)