my error log while upgrading

[Wed Jul 19 18:02:23.886813 2017] [:error] [pid 18859] [client 47.15.12.60:63795] PHP Fatal error: Uncaught Exception: Error: Could not load template adaptor ! in /var/www/html/system/storage/modification/system/library/template.php:17\nStack trace:\n#0 /var/www/html/system/storage/modification/system/engine/loader.php(92): Template->__construct(NULL)\n#1 /var/www/html/install/controller/common/header.php(14): Loader->view('common/header', Array)\n#2 /var/www/html/system/storage/modification/system/engine/action.php(51): ControllerCommonHeader->index(Array)\n#3 /var/www/html/system/storage/modification/system/engine/loader.php(35): Action->execute(Object(Registry), Array)\n#4 /var/www/html/install/controller/upgrade/upgrade.php(28): Loader->controller('common/header')\n#5 /var/www/html/system/storage/modification/system/engine/action.php(51): ControllerUpgradeUpgrade->index()\n#6 /var/www/html/system/engine/router.php(34): Action->execute(Object(Registry))\n#7 /var/www/html/system/engine/router.php(29): Router->execute(Object(Action))\n#8 /var/www/html/system/framework.php(168): Router->dispatch(Object(Action), Obje in /var/www/html/system/storage/modification/system/library/template.php on line 17
also getting 500 error even i cant login, any help? i am upgrading 2.3.0.2 to 3.0.2

any help?

It seems that your existing site has theme or extensions which are not compatible with OpenCart 3. You should confirm this problem with extension developer.

with the default theme still error