Temporarily skip failing tests due to dependency change
cc @sgugger @stas00 
@julien-c wrote that test
https://github.com/huggingface/transformers/pull/3800/files#diff-d524f2b47fd9e3af8aea82b9fac55079R88-R90
so it's probably a good idea to ping him instead, as I'm unfamiliar, yet, with that part of `transformers`.