chore(type): specify that programError() never returns, aiding typing

This extra type spec means we don't have to add 'undefined' to functions
that don't explicitly return when calling programError()

src/lib/programError.ts

@@ -2,7 +2,7 @@ import { print } from '../lib/logging'
 import { Options } from '../types/Options'
 
 /** Print an error. Exit the process if in CLI mode. */
-function programError(options: Options, message: string) {
+function programError(options: Options, message: string): never {
   if (options.cli) {
     print(options, message, null, 'error')
     process.exit(1)