client.contact_list: throws exception

client = ::MessageBird::Client.new(access_key)
client.contact_list

Returns 

```
MessageBird::ErrorException: MessageBird::ErrorException
from /Users/User/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/messagebird-rest-1.4.2/lib/messagebird/client.rb:56:in `parse_body'
```