After the upgrade Xcode 10.3 XiB package wrong, suggesting:
Failed to find or create execution context for description '<IBCocoaTouchPlatformToolDescription: 0x7fefbefd1d80> System content for IBCocoaTouchFramework-EightAndLater <IBScaleFactorDeviceTypeDescription: 0x7fefbebf4f70> scaleFactor=2x'. These intermediate objects were non-nil: (
A terminal command to solve the problem
sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService