Use Xenial for gd support.
Use Xenial for gd support.

Error message:
    Your requirements could not be resolved to an installable set of packages.
    Problem 1
        - The requested PHP extension ext-gd * is missing from your system. Install or enable PHP's gd extension.

php-curl-class/php-curl-class,php-curl-class/php-curl-class,php-curl-class/php-curl-class,zachborboa/php-curl-class,zachborboa/php-curl-class,zachborboa/php-curl-class