Support python 3

Signed-off-by: Daniel Nephin <dnephin@gmail.com>

compose/progress_stream.py

@@ -1,6 +1,7 @@
 import codecs
 import json
-import os
+
+import six
 
 
 class StreamOutputError(Exception):
@@ -8,8 +9,9 @@ class StreamOutputError(Exception):
 
 
 def stream_output(output, stream):
-    is_terminal = hasattr(stream, 'fileno') and os.isatty(stream.fileno())
-    stream = codecs.getwriter('utf-8')(stream)
+    is_terminal = hasattr(stream, 'isatty') and stream.isatty()
+    if not six.PY3:
+        stream = codecs.getwriter('utf-8')(stream)
     all_events = []
     lines = {}
     diff = 0
@@ -55,7 +57,6 @@ def print_output_event(event, stream, is_terminal):
         # erase current line
         stream.write("%c[2K\r" % 27)
         terminator = "\r"
-        pass
     elif 'progressDetail' in event:
         return