Checking instance exists in master._get_cached_minion_data when cache.fetch returns None

salt/cache/__init__.py

@@ -143,8 +143,8 @@ class Cache(object):
             added by the driver itself.
 
         :return:
-            Return a python object fetched from the cache or None if the given
-            path or key not found.
+            Return a python object fetched from the cache or and empty dict if 
+            the given path or key not found.
 
         :raises SaltCacheError:
             Raises an exception if cache driver detected an error accessing data

salt/cache/consul.py

@@ -104,7 +104,7 @@ def fetch(bank, key):
     try:
         _, value = api.kv.get(c_key)
         if value is None:
-            return value
+            return {}
         return __context__['serial'].loads(value['Value'])
     except Exception as exc:
         raise SaltCacheError(

salt/cache/localfs.py

@@ -61,7 +61,7 @@ def fetch(bank, key, cachedir):
     key_file = os.path.join(cachedir, os.path.normpath(bank), '{0}.p'.format(key))
     if not os.path.isfile(key_file):
         log.debug('Cache file "%s" does not exist', key_file)
-        return None
+        return {}
     try:
         with salt.utils.fopen(key_file, 'rb') as fh_:
             return __context__['serial'].load(fh_)