Normally, jinja2 render_template method asks a string of a full path of html. I do as the format below but it still raise the error.
render_template('/var/www/xyz/template/_base_front.html', {"data":"pc"})
I try opening the path by using nano editor, it works fine.
A particular file is full permission of read, write, and execute.

you need to place the file in the
templatesfolder (default folder if you didn't define your owntemplate_folder) and provide a relative path to it (probably_base_front.htmlin your case).from documentation: