Why won't my Swift-backed Preference Pane load?

Question

I am trying to create a custom System Preferences pane for my app. However, when I try to load it to test, I get this in the Console:

Apr 26 17:16:17 computer-name System Preferences[8545]: dlopen_preflight failed with dlopen_preflight(/Users/username/Library/PreferencePanes/App Name.prefPane/Contents/MacOS/App Name): Library not loaded: @rpath/libswiftAppKit.dylib
      Referenced from: /Users/username/Library/PreferencePanes/App Name.prefPane/Contents/MacOS/App Name
      Reason: image not found for /Users/username/Library/PreferencePanes/App Name.prefPane

It seems like the Swift wrapper for AppKit failed to load... something I'm sure I need. So what happened here and how do I fix it?