If specify non-existed file with --file option, mocha throw expection.

./bin/mocha --file non-existed
/Users/mocha/node_modules/yargs/yargs.js:1163
      else throw err
           ^

Error: Cannot find module '/Users/mocha/non-existed'
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:582:15)
    at Function.Module._load (internal/modules/cjs/loader.js:508:25)
    at Module.require (internal/modules/cjs/loader.js:637:17)
    at require (internal/modules/cjs/helpers.js:22:18)
    at /Users/mocha/lib/mocha.js:309:36
    at Array.forEach (<anonymous>)
    at Mocha.loadFiles (/Users/mocha/lib/mocha.js:306:14)
    at Mocha.run (/Users/mocha/lib/mocha.js:784:10)
    at Object.exports.singleRun (/Users/mocha/lib/cli/run-helpers.js:108:16)
    at exports.runMocha (/Users/mocha/lib/cli/run-helpers.js:143:13)
    at Object.exports.handler.argv [as handler] (/Users/mocha/lib/cli/run.js:305:3)
    at Object.runCommand (/Users/mocha/node_modules/yargs/lib/command.js:242:26)
    at Object.parseArgs [as _parseArgs] (/Users/mocha/node_modules/yargs/yargs.js:1104:24)
    at Object.parse (/Users/mocha/node_modules/yargs/yargs.js:566:25)
    at Object.exports.main (/Users/mocha/lib/cli/cli.js:68:6)
    at Object.<anonymous> (/Users/mocha/bin/mocha:131:29)
    at Module._compile (internal/modules/cjs/loader.js:701:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:712:10)
    at Module.load (internal/modules/cjs/loader.js:600:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:539:12)
    at Function.Module._load (internal/modules/cjs/loader.js:531:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:754:12)
    at startup (internal/bootstrap/node.js:283:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:622:3)

It should be handled like --require.

./bin/mocha --require non-existed
mocha inspect [spec..]

Run tests with Mocha

Rules & Behavior
  --allow-uncaught           Allow uncaught errors to propagate        [boolean]

...

  --list-interfaces  List built-in user interfaces & exit              [boolean]
  --list-reporters   List built-in reporters & exit                    [boolean]

✖ ERROR: Cannot find module 'non-existed'