How to read the error code in console output from Jenkins pipeline script

Thanks Bonibom, for your reply. I have updated my script but still I am getting the following error.

Script in pipeline:

pipeline{
agent {label "windows"}
stages {
stage('Test complete'){

steps {
git credentialsId: 'GitHub-RAVEn', url: 'https://github.com/smoke-tests.git', branch: 'master'
withVault(configuration: [timeout: 60, vaultUrl: 'https://vault.com'],
vaultSecrets: [[engineVersion: 1, path: 'secret//testing',
secretValues: [[envVar: 'USERNAME', vaultKey: 'username'], [envVar: 'PASSWORD', vaultKey: 'password']]]]) {
testcompletetest commandLineArguments: "/run /SilentMode /psv:env=prod /psv:ADFSusername=${USERNAME} /psv:ADFSpassword=${PASSWORD}", generateMHT: true, launchType: 'lcProject', project: 'CORE_Prod_Smoke', suite: 'Prod_SmokeTest.pjs'
}
}
}
stage('Checking log'){
steps{
script{
List<String> log= currentBuild.rawBuild.getLog(100).contains("exit code: 0")
for (String line : log)
{
if (line.contains("Test runner exit code: 0"))
{
echo 'aborted'
emailext (
subject: "Core application Failed to login in Prod",
body: "Core application seems to be failed to login in Prod. Please click the link to access the test results for more details \n" + env.BUILD_URL+"TestComplete/",
to: 'vinod.k.tanguturi@associates.com',
from: "donotreply@cloudbees.com")
}
}
}
}
}
}

Error in console

[GitHub Checks] GitHub check (name: Jenkins, status: COMPLETED) has been published.
org.jenkinsci.plugins.scriptsecurity.sandbox.RejectedAccessException: Scripts not permitted to use method hudson.model.Run getLog int
	at org.jenkinsci.plugins.scriptsecurity.sandbox.whitelists.StaticWhitelist.rejectMethod(StaticWhitelist.java:265)
	at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:161)
	at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:161)
	at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:165)
	at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.methodCall(SandboxInvoker.java:17)
	at WorkflowScript.run(WorkflowScript:18