What is this error "No localized files found for language Base"?

Issue

When using the iOS screenshot plugin, I get this error "No localized files found for language Base". But my strings file is there, why isn't the plugin detecting it?

Answer

Base.lproj should only contain IB files (e.g. .storyboard and .xib). Check to see if your strings file is placed in the correct place. The Localizeable.strings for English should be placed under en.lproj. Base is not a supported locale by iOS and our plugin.

For more information, please go to: https://developer.apple.com/library/ios/documentation/MacOSX/Conceptual/BPInternational/MaintaingYourOwnStringsFiles/MaintaingYourOwnStringsFiles.html