=== modified file 'aptsources/distro.py'
--- aptsources/distro.py	2014-10-24 10:16:01 +0000
+++ aptsources/distro.py	2015-08-13 10:53:41 +0000
@@ -484,11 +484,11 @@
 
 def _system_image_channel():
     """Get the current channel from system-image-cli -i if possible."""
-    from subprocess import Popen, PIPE
+    from subprocess import Popen, PIPE, DEVNULL
     import errno
     try:
         out = Popen(
-            ['system-image-cli', '-i'], stdout=PIPE,
+            ['system-image-cli', '-i'], stdout=PIPE, stderr=DEVNULL,
             universal_newlines=True).communicate()[0]
         for l in out.splitlines():
             if l.startswith('channel: '):