Currently 8.x fails to install if you are using MyISAM as database driver.
Syntax error or access violation: 1071 Specified key was too long; max key length is 1000 bytes: CREATE TABLE {file_usage} ( `fid` INT unsigned NOT NULL COMMENT 'File ID.', `module` VARCHAR(255) NOT NULL DEFAULT '' COMMENT 'The name of the module that is using the file.', `type` VARCHAR(64) NOT NULL DEFAULT '' COMMENT 'The name of the object type in which the file is used.', `id` VARCHAR(64) NOT NULL DEFAULT 0 COMMENT 'The primary key of the object using the file.', `count` INT unsigned NOT NULL DEFAULT 0 COMMENT 'The number of times this file is used by this object.', PRIMARY KEY (`fid`, `type`, `id`, `module`), INDEX `type_id` (`type`, `id`), INDEX `fid_count` (`fid`, `count`), INDEX `fid_module` (`fid`, `module`) ) ENGINE = InnoDB DEFAULT CHARACTER SET utf8 COMMENT 'Track where a file is used.'; Array ( )
This means that the key/index of the file_usage table is too long (longer than 1000bytes) for MyISAM.
This can be easily reproduced on simplytest.me as it uses MyISAM: http://simplytest.me/project/drupal/8.x