Add more checks on the release file.

Jenkinsfile

@@ -1,7 +1,11 @@
 import groovy.json.JsonSlurper
 
+//check and parse the release file
 def inputFile = new File(".\releases\gcube-${params.gCube_release_number}.json")
+assert inputFile.exists() : "Release file not found (expected gcube-${params.gCube_release_number}.json)"
+assert inputFile.canRead() : "Release file cannot be read"
 def gcubeJSON = new JsonSlurper().parseText(inputFile)
+
 //check that the release number parameter is the one expected
 assert gcubeJSON["gCube.version"] == params.gCube_release_number : "Release versions do not match!"
 
@@ -47,13 +51,13 @@ echo "Use settings file at ${maven_settings_file}"
 echo "Use local repo at ${maven_local_repo_path}"
 echo "Release number: ${params.gCube_release_number}"
 
-def apps = gcubeJSON['Components']
+def components = gcubeJSON['Components']
 
 def dynamicStages = [:]
 
 //let's build the stages closures
-apps.each { entry -> echo "App name: $entry.key = Jobs: $entry.value" }
-apps.each { entry ->
+components.each { entry -> echo "App name: $entry.key = Jobs: $entry.value" }
+components.each { entry ->
     def app = entry.key
     dynamicStages["stage-${app}"] = ["${app}":{
            node {