I have no problem testing SwiftyDropbox on my device when my Dropbox language on the site is set to English. But if I go to settings and change the language to Swedish or Dutch, the app crashes in getting the usersGetCurrentAccount() method, giving the following error:
precondition failed: "sv-SE" must be at most 2 characters: file /Users/HenkMac/Desktop/Xcode/BudEye Calendar/Pods/SwiftyDropbox/Source/BabelValidators.swift, line 5

I'm not sure if this happened before iOS9, but the only way to fix this at the moment is settings the language to English in the account settings of Dropbox.