Fix lint errors.

dev_mode/webpack.config.js

@@ -8,7 +8,7 @@ var fs = require('fs-extra');
 var Handlebars = require('handlebars');
 var HtmlWebpackPlugin = require('html-webpack-plugin');
 var webpack = require('webpack');
-var DuplicatePackageCheckerPlugin = require("duplicate-package-checker-webpack-plugin");
+var DuplicatePackageCheckerPlugin = require('duplicate-package-checker-webpack-plugin');
 
 var Build = require('@jupyterlab/buildutils').Build;
 var package_data = require('./package.json');

jupyterlab/staging/webpack.config.js

@@ -8,7 +8,7 @@ var fs = require('fs-extra');
 var Handlebars = require('handlebars');
 var HtmlWebpackPlugin = require('html-webpack-plugin');
 var webpack = require('webpack');
-var DuplicatePackageCheckerPlugin = require("duplicate-package-checker-webpack-plugin");
+var DuplicatePackageCheckerPlugin = require('duplicate-package-checker-webpack-plugin');
 
 var Build = require('@jupyterlab/buildutils').Build;
 var package_data = require('./package.json');

tests/webpack.config.js

@@ -1,4 +1,3 @@
-var path = require('path');
 var ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');
 
 var cpus = require('os').cpus().length;