Getting error when updating Epic status

[Swarna Radha]

Hi,

I want to update the epic status when transitioning from to do to in progress.

I have written a script:

import com.atlassian.jira.ComponentManager;
import com.atlassian.jira.issue.CustomFieldManager;
import com.atlassian.jira.issue.customfields.manager.OptionsManager;
import com.atlassian.jira.issue.fields.CustomField;
import com.atlassian.jira.issue.IssueManager;
import com.atlassian.jira.issue.MutableIssue;
import com.atlassian.jira.issue.Issue;
import com.atlassian.jira.user.ApplicationUser;
import com.atlassian.jira.component.ComponentAccessor

def issueManager = ComponentAccessor.getIssueManager()
def user= ComponentAccessor.getJiraAuthenticationContext().getLoggedInUser()
if (issue.issueType.name == "Epic")
{
CustomField epicStatus = customFieldManager.getCustomFieldObjectByName("Epic Status");
//FieldConfig epicStatusFieldConfig = epicStatus.getRelevantConfig(issue);
// OptionsManager optionsManager = ComponentManager.getComponentInstanceOfType(OptionsManager.class)
// Options epicStatusOptions = optionsManager.getOptions(epicStatusFieldConfig);
//Option epicStatusDoneOption = epicStatusOptions.getOptionForValue("In Progress", null);
MutableIssue issueToUpdate = (MutableIssue) issue;
issueToUpdate.setCustomFieldValue(epicStatus, "In Progress");
//The updateIssue is actually not needed
// issueManager.updateIssue(user, issueToUpdate, EventDispatchOption.ISSUE_UPDATED, false);
}

But I am getting the following error after execution: 

Time (on server): Tue Jan 08 2019 10:54:52 GMT+0400 (Gulf Standard Time)

The following log information was produced by this execution. Use statements like:log.info("...") to record logging information.

2019-01-08 10:54:52,776 ERROR [workflow.ScriptWorkflowFunction]: *************************************************************************************
2019-01-08 10:54:52,776 ERROR [workflow.ScriptWorkflowFunction]: Script function failed on issue: PROJ-3962, actionId: 11, file: <inline script>
groovy.lang.MissingPropertyException: No such property: customFieldManager for class: Script207
	at Script207.run(Script207.groovy:22  

Kindly advice.

Thanks
Swarna