fix(server): use flatted for json.stringify

Remove json3 dep and use, probably was needed for older node code.
Fixes #3215

lib/server.js

@@ -8,6 +8,8 @@ const spawn = require('child_process').spawn
 const tmp = require('tmp')
 const fs = require('fs')
 const path = require('path')
+const {stringify} = require('flatted/cjs')
+
 const BundleUtils = require('./utils/bundle-utils')
 const NetUtils = require('./utils/net-utils')
 const root = global || window || this
@@ -63,7 +65,7 @@ class Server extends KarmaEventEmitter {
 
     const config = cfg.parseConfig(cliOptions.configFile, cliOptions)
 
-    this.log.debug('Final config', JSON.stringify(config, null, 2))
+    this.log.debug('Final config', stringify(config, null, 2))
 
     let modules = [{
       helper: ['value', helper],

package.json

@@ -412,6 +412,7 @@
     "eslint-plugin-promise": "^3.4.2",
     "eslint-plugin-react": "^7.0.1",
     "eslint-plugin-standard": "^3.0.1",
+    "flatted": "^2.0.0",
     "grunt": "^1.0.0",
     "grunt-auto-release": "^0.0.7",
     "grunt-browserify": "^5.0.0",
@@ -428,7 +429,6 @@
     "http2": "^3.3.6",
     "husky": "^0.14.3",
     "jasmine-core": "^2.3.4",
-    "json3": "^3.3.2",
     "karma-browserify": "^5.0.1",
     "karma-browserstack-launcher": "^1.0.0",
     "karma-chai": "^0.1.0",

test/client/karma.spec.js

@@ -1,6 +1,5 @@
 // shim all the things
 require('core-js/es5')
-global.JSON = require('json3')
 var sinon = require('sinon')
 var assert = require('assert')