With introduction of threading in 4.42.0, I can no longer cache the results of gateway.customer.find() in redis (which pickles the object)

`customer = gateway.customer.find("the_id_of_customer")`

Try to store the result of this in redis to be used later.

`cache.set("braintree_customer_id", customer, 60*60*24)`

This is because `customer` now represents a thread-local object, before it did not. Redis tries to pickle the object for storage but it can not pickle a thread-local object.
