After update to 2.2.1 I get next error:
main.INFO: Cache file with merged layout: LAYOUT_adminhtml_STORE2_391fccd54da687afc76a5d6559b714906 and handles default, adminhtml_dashboard_index: Please correct the XML data and try again. Element 'css': This element is not expected. Line: 4
Did magento 2.2 change layout XML syntax?
How to debug this issue? How to find out which file has wrong syntax?
I'm not completely sure but I've tracked some similiar issues to https://magento.stackexchange.com/questions/199151/magento-2-2-0-upgrade-error-attribute-type-is-not...
Can you check if this is useful?