Migre um fórum Vanilla para Discourse

So… I’m trying to import a forum from YAF. I’ve passed through vanilla and I’m trying to follow these instructions.
I’m running on a bitnami dicourse vm (bitnami-discourse-1.5.3-1-r28-linux-ubuntu-14.04-x86_64).
I’ve come to step 5 :
RAILS_ENV=production ruby script/import_scripts/vanilla.rb /shared/export.txt

I get the following error:
You are running an old version of bundler, please upgrade bundler ASAP, if you are using Discourse docker, rebuild your container.
and
script/import_scripts/vanilla.rb:82:in import_users': undefined method ’ for nil:NilClass (NoMethodError)
from script/import_scripts/vanilla.rb:19:in execute' from /opt/bitnami/apps/discourse/htdocs/script/import_scripts/base.rb:45:in perform’
from script/import_scripts/vanilla.rb:254:in `’
The bundler version installed in the vm is Bundler version 1.10.4

I don’t get the impression that the bundler error is fatal, but the final error is confusing me. any help here would be appreciated.

Update – if I setup an development environment like described here : Discourse as Your First Rails App | BlogDiscourse
I stil get the same fatal error …
script/import_scripts/vanilla.rb:82:in import_users': undefined method ’ for nil:NilClass (NoMethodError)
from script/import_scripts/vanilla.rb:19:in execute' from /opt/bitnami/apps/discourse/htdocs/script/import_scripts/base.rb:45:in perform’
from script/import_scripts/vanilla.rb:254:in `’