Current "Install and Administration Guide for OpenEMM 2015" V1.3.2-20170223 doesn't specify where you have to set database settings in case you aren't running a local MySQL instance and/or are using non-default credentials.
While you will be able to get OpenEMM 2015 R3 basically up and running when you only adjust the Resource entries in conf/context.xml (frontend works, you are able to send out mails) you will probably ignore the message
which will popup when you execute openemm.sh start.Failed to setup database interface
So basically just editing conf/context.xml isn't enough.
However, agn.py seems to expect names from a previous version. I.e. it is reading from webapps/openemm/WEB-INF/classes/emm.properties but expects keys like jdbc.username and not jdbc.openemmDB.*.
Please get this sorted. Best thing would be to have one place where you manage these settings. Imagine you have to change them later and have to remember all the places... Finally, please consider adding a paragraph to the documentation which explains where you have to set these things.