Unable to show the error message for required condition

Summary

Unable to show the error message for required condition

Content

Hi Team,

I have business scenario for particular BU the Primary contact should show as Mandatory. So for this I have placed groovy script in field level but when I miss the Primary contact it shows the System generated error message I need customized pop-up message as "Primary Contact is Required" but currently it shows like this below picture

Error
	Messages for this page are listed below. Attribute ContactName in OpportunityAM.oracle_apps_sales_opptyMgmt_opportunities_opportunityService_applicationModule_OpportunityAM.Opportunity is required. Primary Contact Attribute KeyContactId in OpportunityAM.oracle_apps_sales_opptyMgmt_opportunities_opportunityService_applicationModule_OpportunityAM.Opportunity is require