title: Braintree: Authorization Error when creating or updating a customer with a CVV verification in Sandbox mode
body: <p>I am using <code>Braintree</code> as a payment gateway of my iOS app.<br>
  I created a Node.js server to process the payment.<br>
  I want to create customers with the customer id of the user id used in the user management system.</p>
  
  <pre><code>BraintreeGateway.customer.update(req.uid, {
    paymentMethodNonce,
    verifyCard: process.env.NODE_ENV === 'production'
  }, (err, result) =&gt; {
    if (err) {
      next(err);
    } else {
      if (result.success) {
        req.customer = result.customer
        console.info('Payment Method:', result.customer.paymentMethods[0])
        res.send({
          status: HttpStatus.OK,
          message: 'Successfully updated!'
        })
      } else {
        next({
          error: 'Failed to update a payment method!',
          result
        })
      }
    }
  })
  </code></pre>
  
  <p>Here <code>req.uid</code> is the unique identifier of the user.<br>
  It is working well without CVV verification settings enabled in the Braintree Control Panel. <a href="https://sandbox.braintreegateway.com/merchants/~/processing" rel="nofollow noreferrer">Here</a><br>
  But with the CVV verification settings enabled, I get <code>authorizationError: Authorization Error</code> which means the invalid API key.<a href="https://developers.braintreepayments.com/reference/general/exceptions/node#authorization-error" rel="nofollow noreferrer">Here</a><br>
  I am using <code>DropIn UI</code> to input credit card and passing the <code>paymentMethodNonce</code> to the server properly.<br>
  The current test credit card number is Number: <code>4242 4242 4242 4242</code> Exp: <code>12/2019</code> CVV: <code>123</code>.</p>
  
  <p>What is the mistake here? Will it work in the production mode? (Braintree will accept the valid credit card numbers in the production mode? )</p>