PFTwitterUtils should be initialized after setting up Parse.
I had a look at the SDK source code and the assert made is that Parse is first set up using an application id and a client key. But according to the open sourced server documentation the client key is an optional configuration argument. So if you do not provide it, it will always fail.
I created a pull request but in the meantime, a workaround is to pass a dummy client key to the Parse SDK initializer. 02/25/2016