If you've been getting this error on OSX Appium when running tests for iOS:
Error: Unable to launch WebDriverAgent because of xcodebuild failure: "ENOENT: no such file or directory, open '/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/appium-xcuitest-driver/WebDriverAgent/PrivateHeaders/XCTest/XCUICoordinate.h'".
cd /Applications/Appium.app/Contents/Resources/app ; npm install
This should install the missing requirements and fix your issue. Hopefully this dependancy step gets patched soon.