Refactoring to use a common node class for all VMs and other (future) objects.

gns3server/compute/docker/docker_error.py

@@ -19,10 +19,10 @@
 Custom exceptions for the Docker module.
 """
 
-from ..vm_error import VMError
+from ..node_error import NodeError
 
 
-class DockerError(VMError):
+class DockerError(NodeError):
     pass