Add vault to module dependencies
You need to add dependencies on the Magento_Vault module in the payment method’s composer.json and module.xml files.
Example: adding Vault module dependencies for the Braintree payment method
app/code/Magento/Braintree/composer.json:
{
"name": "magento/module-braintree",
...
"require": {
...
"magento/module-vault": "100.1.*"
...
}
...
}app/code/Magento/Braintree/etc/module.xml:
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
<module name="Magento_Braintree" setup_version="2.0.0">
<sequence>
...
<module name="Magento_Vault"/>
...
</sequence>
</module>
</config>