replaced promises with async/await

libs/util.js

@@ -1,29 +1,31 @@
 const realpath = require('fs').realpath;
 const stat = require('fs').stat;
 
-function fileExists(file) {
-    return new Promise((resolve, reject) => {
+async function fileExists(file) {
     if (file === undefined) {
-            reject('can not check the existence of an undefined file');
+        throw new Error('can not check the existence of an undefined file');
     }
-        resolvePath(file)
-            .then((path) => {
+    let path;
+    try {
+        path = await resolvePath(file);
+    } catch (err) {
+        throw err;
+    }
+    return await new Promise((resolve, reject) => {
         stat(path, (err, stats) => {
             if (err) {
                 reject(err);
             }
             resolve({path, stats});
         })
-            })
-            .catch(reject);
     });
 }
 
-function resolvePath(file) {
-    return new Promise((resolve, reject) => {
+async function resolvePath(file) {
     if (file === undefined) {
-            reject('can not resolve a path to an undefined file');
+        throw new Error('can not resolve a path to an undefined file');
     }
+    return await new Promise((resolve, reject) => {
         realpath(file, (err, resolvedPath) => {
             if (err) {
                 reject('resolving path \'' + file + '\' encountered an error >>> ' + err);