How to convert vBulletin 4 database to Discourse?

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I did the following steps:

[root@disc3 ~]# cd /var/discourse
[root@disc3 discourse]# ./launcher enter app
which: no docker.io in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin)

And after I added the mysql gem to gemfile

root@disc3-app:/var/www/discourse# echo "gem 'mysql2'" >> Gemfile
root@disc3-app:/var/www/discourse# sudo gem install mysql2
Building native extensions.  This could take a while...
Successfully installed mysql2-0.4.4
1 gem installed

Something surprising happened when I did the bundle install:

root@disc3-app:/var/www/discourse# bundle install --no-deployment
Don't run Bundler as root. Bundler can ask for sudo if it is needed, and installing your bundle as
root will break this application for all non-root users on this machine.
Fetching gem metadata from https://rubygems.org/............
Fetching version metadata from https://rubygems.org/..
Fetching dependency metadata from https://rubygems.org/.
Resolving dependencies...
Installing rake 11.2.2
Installing i18n 0.7.0
**_[...]_**
Bundle complete! 100 Gemfile dependencies, 179 gems now installed.
Gems in the group development were not installed.
Use `bundle show [gemname]` to see where a bundled gem is installed.
Post-install message from certified:
IMPORTANT: Remember to use the included executable `certifed-update` regularly to keep your certificate bundle up to date.

179 gems installed, wow.
But when I try to start the converter, this happens:

root@disc3-app:/var/www/discourse# bundle exec ruby script/import_scripts/vbulletin.rbURGENT: FATAL:  Peer authentication failed for user "discourse"
 Failed to initialize site default
/usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/postgresql_adapter.rb:651:in `initialize': FATAL:  Peer authentication failed for user "discourse" (PG::ConnectionBad)
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/postgresql_adapter.rb:651:in `new'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/postgresql_adapter.rb:651:in `connect'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/postgresql_adapter.rb:242:in `initialize'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/postgresql_adapter.rb:44:in `new'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/postgresql_adapter.rb:44:in `postgresql_connection'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:438:in `new_connection'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:448:in `checkout_new_connection'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:422:in `acquire_connection'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:349:in `block in checkout'
        from /usr/local/lib/ruby/2.3.0/monitor.rb:214:in `mon_synchronize'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:348:in `checkout'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:263:in `block in connection'
        from /usr/local/lib/ruby/2.3.0/monitor.rb:214:in `mon_synchronize'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:262:in `connection'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:571:in `retrieve_connection'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_handling.rb:113:in `retrieve_connection'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_handling.rb:87:in `connection'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/attributes.rb:93:in `columns'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/attributes.rb:98:in `columns_hash'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/core.rb:173:in `block in find_by'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/core.rb:173:in `each'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/core.rb:173:in `all?'
        from /usr/local/lib/ruby/gems/2.3.0/gems/activerecord-4.2.7.1/lib/active_record/core.rb:173:in `find_by'
        from /var/www/discourse/lib/discourse.rb:282:in `system_user'
        from /var/www/discourse/script/import_scripts/base.rb:477:in `<class:Base>'
        from /var/www/discourse/script/import_scripts/base.rb:20:in `<top (required)>'
        from script/import_scripts/vbulletin.rb:2:in `require'
        from script/import_scripts/vbulletin.rb:2:in `<main>'