installed plugins are placed in a directory relative to where gremlin.sh is started

From mailing list discussion here https://groups.google.com/d/msg/gremlin-users/4ooHKOXo7-w/1xmMQZvQCwAJ

The problem is that if you start gremlin.sh from the $TP3_HOME/bin directory, installed plugins end up under $TP3_HOME/bin/ext instead of under $TP3_HOME/ext where existing plugins are located.

The problem also exists with gremlin-server.sh plugins.

The workaround is to start gremlin from $TP3_HOME with ./bin/gremlin.sh