[Bitrix\Main\DB\ConnectionException] 
Mysql connect error [localhost]: (2002) Connection refused (400)
/home/bitrix/www/bitrix/modules/main/lib/db/mysqliconnection.php:65
#0: Bitrix\Main\DB\MysqliConnection->connectInternal()
	/home/bitrix/www/bitrix/modules/main/lib/data/connection.php:53
#1: Bitrix\Main\Data\Connection->getResource()
	/home/bitrix/www/bitrix/modules/main/lib/db/mysqlisqlhelper.php:21
#2: Bitrix\Main\DB\MysqliSqlHelper->forSql(string)
	/home/bitrix/www/bitrix/modules/main/lib/config/option.php:193
#3: Bitrix\Main\Config\Option::load(string)
	/home/bitrix/www/bitrix/modules/main/lib/config/option.php:38
#4: Bitrix\Main\Config\Option::get(string, string, string, string)
	/home/bitrix/www/bitrix/modules/main/classes/general/option.php:30
#5: CAllOption::GetOptionString(string, string, string, string)
	/home/bitrix/www/bitrix/modules/learning/include.php:8
#6: include_once(string)
	/home/bitrix/www/bitrix/modules/main/lib/loader.php:177
#7: Bitrix\Main\Loader::includeModuleInternal(string)
	/home/bitrix/www/bitrix/modules/main/lib/loader.php:137
#8: Bitrix\Main\Loader::includeModule(string)
	/home/bitrix/www/local/php_interface/include/function.php:10
#9: require_once(string)
	/home/bitrix/www/local/php_interface/init.php:15
#10: include_once(string)
	/home/bitrix/www/bitrix/modules/main/include.php:241
#11: require_once(string)
	/home/bitrix/www/bitrix/modules/main/include/prolog_before.php:14
#12: require_once(string)
	/home/bitrix/www/courses/index.php:2