actually use PKG to determine package type

dvc/updater.py

@@ -48,7 +48,7 @@ class Updater(object):  # pragma: no cover
             logger.debug(msg.format(self.lock.lockfile, action))
 
     def check(self):
-        if os.getenv("CI") or env2bool("DVC_TEST") or env2bool("SNAP"):
+        if os.getenv("CI") or env2bool("DVC_TEST") or PKG == "snap":
             return
 
         self._with_lock(self._check, "checking")

snapcraft.yaml

@@ -31,6 +31,5 @@ apps:
     completer: completion.sh
     environment:
       GIT_PYTHON_GIT_EXECUTABLE: dvc.git
-      SNAP: 1  # suppress update checks
   git:
     command: /usr/bin/git