<?php
namespace XXXCustomerstatusSetup;
use MagentoCustomerSetupCustomerSetupFactory;
use MagentoCustomerModelCustomer;
use MagentoEavModelEntityAttributeSet as AttributeSet;
use MagentoEavModelEntityAttributeSetFactory as AttributeSetFactory;
use MagentoFrameworkSetupInstallDataInterface;
use MagentoFrameworkSetupModuleContextInterface;
use MagentoFrameworkSetupModuleDataSetupInterface;

class InstallData implements InstallDataInterface
{

/**
 * @var CustomerSetupFactory
 */
protected $customerSetupFactory;

/**
 * @var AttributeSetFactory
 */
private $attributeSetFactory;

/**
 * @param CustomerSetupFactory $customerSetupFactory
 * @param AttributeSetFactory $attributeSetFactory
 */
public function __construct(
    CustomerSetupFactory $customerSetupFactory,
    AttributeSetFactory $attributeSetFactory
) {
    $this->customerSetupFactory = $customerSetupFactory;
    $this->attributeSetFactory = $attributeSetFactory;
}

public function install(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
{
    /** @var CustomerSetup $customerSetup */
    $customerSetup = $this->customerSetupFactory->create(['setup' => $setup]);

    $customerEntity = $customerSetup->getEavConfig()->getEntityType('customer');
    $attributeSetId = $customerEntity->getDefaultAttributeSetId();

    /** @var $attributeSet AttributeSet */
    $attributeSet = $this->attributeSetFactory->create();
    $attributeGroupId = $attributeSet->getDefaultGroupId($attributeSetId);

    $customerSetup->addAttribute(Customer::ENTITY, 'custom_customer_status_custom', [
                'type'          => 'int',
                'label'         => 'Custom Customer Status',
                'input'         => 'select',
                'source'        => 'MagentoEavModelEntityAttributeSourceTable',
                'required'      => false,
                'user_defined'  => true,
                'sort_order'    => 11,
                'position'      => 11,
                'system'        => false,
                'option'        => ['values' => ['Awaiting Reply', 'Yes', 'No']],
                'is_used_in_grid'       => true,
                'is_visible_in_grid'    => true,
            ]);

    $attribute = $customerSetup->getEavConfig()->getAttribute(Customer::ENTITY, 'custom_customer_status_custom')
    ->addData([
        'attribute_set_id' => $attributeSetId,
        'attribute_group_id' => $attributeGroupId,
        'used_in_forms' => ['adminhtml_customer'],
    ]);

    $attribute->save();
}
}