Php Version?

We are using CS-Cart 4.5.2.SP2, Cs-cart web site says this version supports up to PHP 7.0.

I installed PHP 7.1 and at quick glance all seems to be working. What type of error should I be looking for. I have PHP set to show all errors. What is supposedly not supported in CS-Cart 4.5.2.SP2 with this version?

I'm not sure if all is working or not.

I did notice i get the following order when trying to view a product using PHP 7.1

Warning: file_get_contents(/home/yada/public_html/store_closed.html): failed to open stream: No such file or directory in /home/yada/public_html/app/Tygh/Development.php on line 112

No error when I use PHP 7.0

Any thoughts on how to fix this error with PHP 7.1 with my cart version?