javax.sql.DataSource case sensitive
Seems that prior to Tomcat 8.0.37 a server.xml like this works:
...
<ResourceLink global='jdbc/DB' name='jdbc/DB' type="javax.sql.Datasource" />
...
But starting with 8.0.37 the case of DataSource is checked and so Datasource stopped working and would result in a ClassNotFound exception. It now has to be DataSource.