Show detailed message of neutron exception

This patch improves the error message by retrieving the more details
from the exception instance. Otherwise, the real error message won't
be displayed (unless using --debug in the command).

Change-Id: I8ba694bda86f7cc8362e301b2044d9b610dde49c

Author: Hongbin Lu

openstackclient/network/common.py

@@ -191,6 +191,8 @@ def take_action(self, parsed_args):
                     self.app.client_manager.compute, parsed_args)
         except openstack.exceptions.HttpException as exc:
             msg = _("Error while executing command: %s") % exc.message
+            if exc.details:
+                msg += ", " + six.text_type(exc.details)
             raise exceptions.CommandError(msg)
 
     def get_parser(self, prog_name):