Convert to Current Swift Syntax Failed - "No such module" (Swift 4, Xcode 9)

I can't find any solution yet.

For now I fix manually setting Swift Language Version

After changing from 3.2 to 4.0 I compile and fix errors and warnings manually.
I'm waiting for a better solution!

I also got this problem while converting my project to Swift 4.0. Looks like problem appears when you try to convert target which imports a framework which is already in Swift 4.0. At your screenshot you try to convert 'RecipeTextParser' which imports 'SovaTools' which is already Swift 4.0.

I found dirty, but working solution. You can use older(Swift 3.2) version of 'SovaTools' when converting. You should NOT check it's mark in target selection window of conversion tool. Then, when 'RecipeTextParser' will be successfully converted you can use Swift 4.0 'SovaTools' version again.

I got this error and in my case one of my Pods(the one Xcode was complaining about) was a Swift 4 target and the rest were Swift 3.2. Looking at the build logs it looks like Xcode built that framework in one location and was searching for it in another. When I reverted that Pod to an older version(that used Swift3.2) the problem went away. Obviously a Xcode bug. HTH