New constraints management.

Co-authored-by: Mathieu Lonjaret <mathieu.lonjaret@gmail.com>

vendor/github.com/vulcand/predicate/predicate.go

@@ -1,3 +1,20 @@
+/*
+Copyright 2014-2018 Vulcand Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+*/
+
 /*
 Predicate package used to create interpreted mini languages with Go syntax - mostly to define
 various predicates for configuration, e.g. Latency() > 40 || ErrorRate() > 0.5.
@@ -76,6 +93,7 @@ type Operators struct {
 
 	OR  interface{}
 	AND interface{}
+	NOT interface{}
 }
 
 // Parser takes the string with expression and calls the operators and functions.