add AddTags, RemoveTags and DescribeTags endpoints to ELB

moto/elb/exceptions.py

@@ -0,0 +1,29 @@
+from __future__ import unicode_literals
+from moto.core.exceptions import RESTError
+
+
+class ELBClientError(RESTError):
+    code = 400
+
+
+class DuplicateTagKeysError(ELBClientError):
+    def __init__(self, cidr):
+        super(DuplicateTagKeysError, self).__init__(
+            "DuplicateTagKeys",
+            "Tag key was specified more than once: {0}"
+            .format(cidr))
+
+
+class LoadBalancerNotFoundError(ELBClientError):
+    def __init__(self, cidr):
+        super(LoadBalancerNotFoundError, self).__init__(
+            "LoadBalancerNotFound",
+            "The specified load balancer does not exist: {0}"
+            .format(cidr))
+
+
+class TooManyTagsError(ELBClientError):
+    def __init__(self):
+        super(TooManyTagsError, self).__init__(
+            "LoadBalancerNotFound",
+            "The quota for the number of tags that can be assigned to a load balancer has been reached")