I have the exact same problem! Except mine says I have scikit-learn version 0.19.1. Based on this post, I downloaded an older version of the classifier from here, but it still gives the same error! Maybe you can try and let me know if this worked for you?
I updated sklearn to the latest version manually, but qiime doesn’t use it because it has it’s own sklearn version within its environment. So at this point apart form upgrading qiime2 and the virtual box, I don’t know what to do. I would appreciate any help!