In Xcode 8.1 GM Release Notes Apple acknowledged the problem and suggested a cleaner workaround:
Keychain APIs may fail to work in the Simulator if your entitlements file doesn’t contain a value for the application-identifier entitlement. (28338972) Workaround: Add a user-defined build setting to your target named ENTITLEMENTS_REQUIRED and set the value to YES. This will cause Xcode to automatically insert an application-identifier entitlement when building.
Note that from what I have tried, it only works in Xcode 8.1. Although the text can mislead you into a build setting, what you need to do is add this to your Environment Variables, in your scheme.
Xcode 8.2 will solve this:
Resolved in Xcode 8.2 beta - IDE Keychain APIs work correctly in Simulator. (28338972)
