Bugfix: specify channel when requesting snap info

debian/changelog

@@ -8,6 +8,8 @@ livecd-rootfs (2.560) UNRELEASED; urgency=medium
   [ Tobias Koch ]
   * When the REPO_SNAPSHOT_STAMP environment variable is set, inject a
     proxy into the build providing a snapshot view of the package repo.
+  * Replace "snap download" with tool that uses snap store's coherence
+    feature.
 
  -- Balint Reczey <rbalint@ubuntu.com>  Mon, 04 Feb 2019 23:02:12 +0700
 

snap-tool

@@ -159,6 +159,7 @@ class Snap:
                     "action":       "download",
                     "instance-key": "0",
                     "name":         self._name,
+                    "channel":      self._channel,
                 }
             ]
         }