Hello/Hi/Greetings,

I'm trying to install piwigo 2.8.5 manually on ubuntu 14.04.5, nginx 1.4.6, php 5.5.9-1ubuntu4.20

I can open the install page.  But when I fill in the form and submit it I get a 500 response from nginx:
HTTP/1.1 500 Internal Server Error
Server: nginx/1.4.6 (Ubuntu)
Date: Sat, 21 Jan 2017 22:22:54 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
X-Powered-By: PHP/5.5.9-1ubuntu4.20

Unfortunately all I get is the 500 (the page is blank), and I can't find any sort of php error log file anywhere.  Nothing useful in /var/log/nginx/error.log, either.

Without an error message it's hard to now what to do next.  Any help greatly appreciated.

Thanks,
Colin

Piwigo version: 2.8.5
PHP version: 5.5.9-1ubuntu4.20
MySQL version: Ver 14.14 Distrib 5.6.33, for debian-linux-gnu (x86_64)
Piwigo URL: http:// N/A