Add the async/await exec wrapper that I use, for an experimental feature.

app/lib/exec/index.js

@@ -0,0 +1,46 @@
+'use strict'
+
+const execRaw = require('child_process').exec
+
+/**
+ * Promisified child_process.exec
+ *
+ * @param cmd
+ * @param arg
+ * @param opts See child_process.exec node docs
+ * @param {stream.Writable} opts.stdout If defined, child process stdout will be piped to it.
+ * @param {stream.Writable} opts.stderr If defined, child process stderr will be piped to it.
+ *
+ * @returns {Promise<{ stdout: string, stderr: stderr }>}
+ */
+async function exec(...args) {
+	let cmd = args[0]
+	let argz = null
+	let opts = null
+	if (typeof args[1] === 'object' && Array.isArray(args[1])) {
+		argz = args[1]
+	}
+	if (argz === null && typeof args[1] === 'object') {
+		opts = args[1]
+	} else if (typeof args[2] === 'object') {
+		opts = args[2]
+	}
+	if (opts === null) {
+		opts = { maxBuffer : 1024 * 1024 }
+	}
+    return new Promise((resolve, reject) => {
+    	const child = execRaw(cmd, opts,
+			(err, stdout, stderr) => err ? reject(err) : resolve({
+				stdout: stdout,
+				stderr: stderr
+			}));
+        if (opts.stdout) {
+            child.stdout.pipe(opts.stdout);
+        }
+        if (opts.stderr) {
+            child.stderr.pipe(opts.stderr);
+        }
+    });
+}
+
+module.exports = exec