Adding fix for issue and validation

Author: fmiquiza

SoftLayer/managers/ticket.py

@@ -5,7 +5,6 @@
 
     :license: MIT, see LICENSE for more details.
 """
-
 from SoftLayer import utils
 
 
@@ -38,6 +37,8 @@ def list_tickets(self, open_status=True, closed_status=True):
                 call = 'getOpenTickets'
             elif closed_status:
                 call = 'getClosedTickets'
+            else:
+                raise ValueError("open_status and closed_status cannot both be False")
 
         return self.client.call('Account', call, mask=mask)