Fatal error: Call to undefined function cache_get() I am getting the following error on the server

Fatal error: Call to undefined function cache_get() in includes/module.inc on line 665
Drush command terminated abnormally due to an unrecoverable error.                                                                                [error]
Error: Call to undefined function cache_get() in includes/module.inc, line 665


How to fix this?
For me, the cause was different: some errors are not caught by Drupal's error handler.

I used a new DateTime() in my settings.php (probably very rare)
It generated an error because the date.timezone setting in my CLI php.ini wasn't set.

To find the real error (this is the interesting part of the answer for all of you, I think) :

Edit your module.inc, line 723.

Add these lines before the cache_get call.

if (!function_exists('cache_get')){ 
    debug_print_backtrace(); 
}
$implementations = cache_get('module_implements', 'cache_bootstrap');


It might give you lots of information about the real source of the issue!