Fix compatibility with node 10

Author: sam-lord

lib/fileRotator.js

@@ -2,7 +2,7 @@ const zlib = require('zlib');
 const {pipeline} = require('stream');
 const {promisify} = require('util');
 const {createReadStream, createWriteStream} = require('fs');
-const fs = require('fs/promises');
+const fs = require('fs').promises;
 const pipe = promisify(pipeline);
 const path = require('path');
 const {processSize} = require('../util/configProcessors');