powerShell optimizatio error handling

lib/util.js

@@ -217,39 +217,55 @@ function getWmic() {
 }
 
 function powerShell(cmd) {
+
+  // helper function
+  function dispose(child) {
     return new Promise((resolve, reject) => {
+      child.stdin.write('exit' + os.EOL);
       process.nextTick(() => {
+        child.stdin.end()
+        child.kill();
+        resolve();
+      });
+    })
+  }
 
   let result = '';
+
+  return new Promise((resolve, reject) => {
+
+    process.nextTick(() => {
+
+      try {
         const child = spawn('powershell.exe', ['-NoLogo', '-InputFormat', 'Text', '-NoExit', '-ExecutionPolicy', 'Unrestricted', '-Command', '-'], {
           stdio: 'pipe'
         });
 
-      if (child) {
+        if (child && child.pid) {
           child.stdout.on('data', function (data) {
             result = result + data.toString('utf8');
           });
           child.stderr.on('data', function (data) {
-          child.kill();
-          reject(data);
+            dispose(child).then(resolve(result));
           });
           child.on('close', function () {
-          child.kill();
-          resolve(result);
+            dispose(child).then(resolve(result));
+            ;
           });
           child.on('error', function () {
-          child.kill();
-          resolve(result);
+            dispose(child).then(resolve(result));
           });
 
           try {
-          child.stdin.write(cmd + '\n');
-          child.stdin.end();
+            child.stdin.write(cmd + os.EOL);
           } catch (e) {
-          reject(result)
+            dispose(child).then(resolve(result));
           }
         } else {
-        reject(result);
+          resolve(result);
+        }
+      } catch (e) {
+        resolve(result);
       }
     });
   });