Raise an error if server flagged as local but should not

If the controller is not started with --local but the server ID
is local it's raise an error.

gns3server/controller/controller_error.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2016 GNS3 Technologies Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+class ControllerError(Exception):
+    def __init__(self, message):
+        super().__init__(message)
+        self._message = message
+
+    def __repr__(self):
+        return self._message
+
+    def __str__(self):
+        return self._message
+
+