JENKINS-52744 Showing meaningful error when an environment variable i…

pipeline-model-definition/src/main/resources/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy

@@ -455,7 +455,7 @@ class ModelInterpreter implements Serializable {
                     "${k}=${v.call()}"
                 }catch (NullPointerException e){
 
-                    throw new IllegalArgumentException(format("Invalid var declared in environment: %s", k))
+                    throw new IllegalArgumentException(format("Invalid variable (%s) declared in environment; There are some problems with its value", k))
                 }
             }.findAll { it != null}
             return {

pipeline-model-definition/src/test/java/org/jenkinsci/plugins/pipeline/modeldefinition/EnvironmentTest.java

@@ -333,7 +333,7 @@ public void notExpressionInEnvironment() throws Exception {
     @Test
     public void improveMessageErrorWhenEnvVarNotExists() throws Exception {
         expect(Result.FAILURE, "improveMessageErrorWhenEnvVarNotExists")
-                .logContains("IllegalArgumentException: Invalid var declared in environment: FOO")
+                .logContains("IllegalArgumentException: Invalid variable (FOO) declared in environment; There are some problems with its value")
                 .go();
     }
 }