Task gitlab:wiki:migrate fails

Created by: krymen

I'm trying to update from 4.2 to 5.0 and unfortunatelly task gitlab:wiki:migrate is failing:

# sudo -u git -H bundle exec rake gitlab:wiki:migrate RAILS_ENV=production

Migrating Wiki for 'nt3.bundles.bank'
Initialized empty Git repository in /home/git/repositories/nt3.bundles.bank.wiki.git/
  Creating page 'Diagram stanów wniosku kredytowego'...
  Created page 'Diagram stanów wniosku kredytowego' [OK]
    Creating revisions...
rake aborted!
undefined method `update' for nil:NilClass
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:93:in `block in create_revisions'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:82:in `each'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:82:in `create_revisions'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:74:in `create_page_and_revisions'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:50:in `block in create_pages'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:49:in `each'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:49:in `create_pages'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:17:in `block in migrate!'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:14:in `each'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:14:in `migrate!'
/home/git/gitlab/lib/tasks/gitlab/migrate_wiki.rake:17:in `block (3 levels) in <top (required)>'

After running again:

# sudo -u git -H bundle exec rake gitlab:wiki:migrate RAILS_ENV=production

Migrating Wiki for 'nt3.bundles.bank'
  Creating page 'Diagram stanów wniosku kredytowego'...
  Failed to create page 'Diagram-stanów-wniosku-kredytowego' [FAILED]
  Creating page 'Definition of Done'...
rake aborted!
incompatible character encodings: UTF-8 and ASCII-8BIT
/home/git/gitlab/vendor/bundle/ruby/1.9.1/gems/grit-2.5.0/lib/grit/index.rb:176:in `%'
/home/git/gitlab/vendor/bundle/ruby/1.9.1/gems/grit-2.5.0/lib/grit/index.rb:176:in `block in write_tree'
/home/git/gitlab/vendor/bundle/ruby/1.9.1/gems/grit-2.5.0/lib/grit/index.rb:171:in `each'
/home/git/gitlab/vendor/bundle/ruby/1.9.1/gems/grit-2.5.0/lib/grit/index.rb:171:in `write_tree'
/home/git/gitlab/vendor/bundle/ruby/1.9.1/gems/grit-2.5.0/lib/grit/index.rb:123:in `commit'
/home/git/gitlab/vendor/bundle/ruby/1.9.1/bundler/gems/gollum-5dcd3c8c8f68/lib/gollum/committer.rb:163:in `commit'
/home/git/gitlab/vendor/bundle/ruby/1.9.1/bundler/gems/gollum-5dcd3c8c8f68/lib/gollum/wiki.rb:327:in `write_page'
/home/git/gitlab/app/models/gollum_wiki.rb:74:in `create_page'
/home/git/gitlab/app/models/wiki_page.rb:168:in `save'
/home/git/gitlab/app/models/wiki_page.rb:127:in `create'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:69:in `create_page_and_revisions'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:50:in `block in create_pages'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:49:in `each'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:49:in `create_pages'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:17:in `block in migrate!'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:14:in `each'
/home/git/gitlab/lib/wiki_to_gollum_migrator.rb:14:in `migrate!'
/home/git/gitlab/lib/tasks/gitlab/migrate_wiki.rake:17:in `block (3 levels) in <top (required)>'