code: function getMandatoryColumnCheck(mandatoryColumns, severity) {
  
  	/**
  	 * @param the coluns found and matched.
  	 */
  	return function (foundColumns) {
  
  		// the header must have all the expected columns but may have more
  		let err = _missingColumns(mandatoryColumns, foundColumns);
  		if (err) {
  			return {
  				errorCode: 'CHECK_HEADER_MANDATORY_COLUMNS',
  				severity: severity,
  				message: 'The following columns are missing in the header and are mandatory: [' + err.join() + ']'
  			};
  		}
  	};
  }
docs: Creates the mandatory column check. This is every time case sensitive as we used the associated column names.
  @param mandatoryColumns The mandatory columns. BUT these are the associated fieldnames, not the original column names
  @param severity The severity if the check fails