Question about v7 -> v8 migration

I'm trying out the v7->v8 migration

I'm not sure what software is needed, or if it's at all important from which path you run the migrate.py.

So please let me know if the cockup is very simple.

I'm running the migration.py from my home folder (instead of the /opt/ installation folder). I don't want to mess that up unless it's necessary.

In my /home/erno/odoo-migration i have

migrate.py
openerp-server.conf
testdb.dump

With command python2.7 migrate.py --config=openerp-server.conf --database=testdb --run-migrations=8.0

Gives me "error message" : No user found in configuration

Why is that? What am I doing wrong here?