Fix bug with vault runner creating token on empty policy

salt/runners/vault.py

@@ -55,6 +55,9 @@ def generate_token(minion_id, signature, impersonated_by_master=False):
                     'num_uses': 1,
                     'metadata': audit_data
                   }
+                  
+        if payload['policies'] == []:
+            return {'error': 'No policies matched minion'}
 
         log.trace('Sending token creation request to Vault')
         response = requests.post(url, headers=headers, json=payload)