Catch exception in snapshot dialog.

gns3server/modules/port_manager.py

@@ -16,7 +16,6 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import socket
-import sys
 import ipaddress
 from aiohttp.web import HTTPConflict
 from gns3server.config import Config