Add proper exception when cannot find tunnel on QEMU, Fixes: #1241

gns3server/compute/qemu/qemu_vm.py

@@ -1144,7 +1144,7 @@ class QemuVM(BaseNode):
                 yield from self.add_ubridge_udp_connection("QEMU-{}-{}".format(self._id, adapter_number),
                                                            self._local_udp_tunnels[adapter_number][1],
                                                            nio)
-            except IndexError:
+            except (IndexError, KeyError):
                 raise QemuError('Adapter {adapter_number} does not exist on QEMU VM "{name}"'.format(name=self._name,
                                                                                                      adapter_number=adapter_number))