NGINX Magento 2.1.3 Setup failed - Bad Gateway - nginx

Question

LEMP STACK (Ubuntu 16.04, Nginx, php7.0-fpm, MariaDB)
Magento 2.1.3 CE Web setup wizard failed.
Output: Failed to load resource: the server responded with a status of
502 (Bad Gateway).
For stack install: https://www.digitalocean.com/community/tutorials/how-to-install-linux-nginx-mysql-php-lemp-stack-in-ubuntu-16-04#step-5-create-a-php-file-to-test-configuration
For nginx virtual block for Magento 2: http://devdocs.magento.com/guides/v2.0/config-guide/multi-site/ms_nginx.html
Nginx Virtual Block file
upstream fastcgi_backend {
server unix:/var/run/php7.0-fpm.sock;
}
server {
listen 80 default_server;
server_name beateli.com www.beateli.com;
set $MAGE_ROOT /var/www/developer/html;
set $MAGE_MODE developer;
include /var/www/developer/html/nginx.conf.sample;
}
nginx.sample.conf file
root $MAGE_ROOT/pub;
index index.php;
autoindex off;
charset UTF-8;
error_page 404 403 = /errors/404.php;
#add_header "X-UA-Compatible" "IE=Edge";
# PHP entry point for setup application
location ~* ^/setup($|/) {
root $MAGE_ROOT;
location ~ ^/setup/index.php {
fastcgi_pass fastcgi_backend;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
include fastcgi_params;
}
location ~ ^/setup/(?!pub/). {
deny all;
}
location ~ ^/setup/pub/ {
add_header X-Frame-Options "SAMEORIGIN";
}
}
# PHP entry point for update application
location ~* ^/update($|/) {
root $MAGE_ROOT;
location ~ ^/update/index.php {
fastcgi_split_path_info ^(/update/index.php)(/.+)$;
fastcgi_pass fastcgi_backend;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param PATH_INFO $fastcgi_path_info;
include fastcgi_params;
}
# Deny everything but index.php
location ~ ^/update/(?!pub/). {
deny all;
}
location ~ ^/update/pub/ {
add_header X-Frame-Options "SAMEORIGIN";
}
}
location / {
try_files $uri $uri/ /index.php?$args;
}
location /pub/ {
location ~ ^/pub/media/(downloadable|customer|import|theme_customization/.*\.xml) {
deny all;
}
alias $MAGE_ROOT/pub/;
add_header X-Frame-Options "SAMEORIGIN";
}
location /static/ {
# Uncomment the following line in production mode
# expires max;
# Remove signature of the static files that is used to overcome the browser cache
location ~ ^/static/version {
rewrite ^/static/(version\d*/)?(.*)$ /static/$2 last;
}
location ~* \.(ico|jpg|jpeg|png|gif|svg|js|css|swf|eot|ttf|otf|woff|woff2)$ {
add_header Cache-Control "public";
add_header X-Frame-Options "SAMEORIGIN";
expires +1y;
if (!-f $request_filename) {
rewrite ^/static/(version\d*/)?(.*)$ /static.php?resource=$2 last;
}
}
location ~* \.(zip|gz|gzip|bz2|csv|xml)$ {
add_header Cache-Control "no-store";
add_header X-Frame-Options "SAMEORIGIN";
expires off;
if (!-f $request_filename) {
rewrite ^/static/(version\d*/)?(.*)$ /static.php?resource=$2 last;
}
}
if (!-f $request_filename) {
rewrite ^/static/(version\d*/)?(.*)$ /static.php?resource=$2 last;
}
add_header X-Frame-Options "SAMEORIGIN";
}
location /media/ {
try_files $uri $uri/ /get.php?$args;
location ~ ^/media/theme_customization/.*\.xml {
deny all;
}
location ~* \.(ico|jpg|jpeg|png|gif|svg|js|css|swf|eot|ttf|otf|woff|woff2)$ {
add_header Cache-Control "public";
add_header X-Frame-Options "SAMEORIGIN";
expires +1y;
try_files $uri $uri/ /get.php?$args;
}
location ~* \.(zip|gz|gzip|bz2|csv|xml)$ {
add_header Cache-Control "no-store";
add_header X-Frame-Options "SAMEORIGIN";
expires off;
try_files $uri $uri/ /get.php?$args;
}
add_header X-Frame-Options "SAMEORIGIN";
}
location /media/customer/ {
deny all;
}
location /media/downloadable/ {
deny all;
}
location /media/import/ {
deny all;
}
# PHP entry point for main application
location ~ (index|get|static|report|404|503)\.php$ {
try_files $uri =404;
fastcgi_pass fastcgi_backend;
fastcgi_buffers 1024 4k;
fastcgi_read_timeout 600s;
fastcgi_connect_timeout 600s;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
include fastcgi_params;
}
gzip on;
gzip_disable "msie6";
gzip_comp_level 6;
gzip_min_length 1100;
gzip_buffers 16 8k;
gzip_proxied any;
gzip_types
text/plain
text/css
text/js
text/xml
text/javascript
application/javascript
application/x-javascript
application/json
application/xml
application/xml+rss
image/svg+xml;
gzip_vary on;
# Banned locations (only reached if the earlier PHP entry point regexes don't match)
location ~* (\.php$|\.htaccess$|\.git) {
deny all;
}