pm2 spawn child EPERM error

I use system under root.
I have a script that successfully runs directly with node but does not work through pm2. It worked before but after installing some updates it does not work anymore (Sadly I'm not sure what exactly I updated because I have noticed the issue afterwards).

That's about spawning child process under root user. I run every command under root user too (node test.js, pm2 start test.js, etc).

PM2 Log output

test-4 (err): Error: spawn EPERM
test-4 (err):     at exports._errnoException (util.js:1026:11)
test-4 (err):     at ChildProcess.spawn (internal/child_process.js:313:11)
test-4 (err):     at exports.spawn (child_process.js:380:9)
test-4 (err):     at exports.execFile (child_process.js:143:15)
test-4 (err):     at /home/www/proxy/test/test.js:9:2
test-4 (err):     at Layer.handle [as handle_request] (/home/www/proxy/node_modules/express/lib/router/layer.js:95:5)
test-4 (err):     at next (/home/www/proxy/node_modules/express/lib/router/route.js:131:13)
test-4 (err):     at Route.dispatch (/home/www/proxy/node_modules/express/lib/router/route.js:112:3)
test-4 (err):     at Layer.handle [as handle_request] (/home/www/proxy/node_modules/express/lib/router/layer.js:95:5)
test-4 (err):     at /home/www/proxy/node_modules/express/lib/router/index.js:277:22

Software versions used

OS         : Ubuntu 16.04.1 LTS
node.js    : 6.9.1
PM2        : 1.1.3

Sample script

test.sh:

#!/usr/bin/env zsh

if [[ $UID != 0 ]]; then
    echo "This must be run as root."
    exit 1
fi

echo $1

fping google.com

test.js:

var express = require("express");
var execFile = require("child_process").execFile;
var path = require("path");

var RDIR = path.dirname(require.main.filename);
var app = express();

app.get("/",function(req,res) {
    execFile(RDIR+"/test.sh",{uid:0},function(err,out,code) {
        console.log(err,out,code);
        res.send(out);
    });
});

app.listen(3017);

Start by reproducing the failure with the provided test.js and test.sh under Ubuntu 16.04. Compare running test.js directly with starting it through PM2, using the listed Node.js and PM2 versions, and inspect the PM2 log and child_process.execFile call. Done means identifying the cause of the EPERM difference and confirming that the sample child process works through PM2 or documenting the incompatibility.