When trying to use a PXE template for windows installation this error occurs. Last known good version 1.15.6.

Here the complete error message:
2018-12-04T15:58:18 [I|app|234b3] Fetching required TFTP boot files for testwin
2018-12-04T15:58:18 [W|app|234b3] Aufgabe Hole TFTP-Bootdateien für testwin.test.loc schlug aufgrund des folgenden Fehlers fehl: undefined method `tr' for #<URI::Generic boot/windows-x86_64-w2k12-X4w09nh2RI/> | Did you mean? try | NoMethodError: undefined method `tr' for #<URI::Generic boot/windows-x86_64-w2k12-X4w09nh2RI/> | Did you mean? try | /usr/share/foreman/app/models/operatingsystems/windows.rb:14:in `pxe_prefix' | /usr/share/foreman/app/models/operatingsystem.rb:200:in `block in pxe_files' | /usr/share/foreman/app/models/operatingsystem.rb:199:in `collect' | /usr/share/foreman/app/models/operatingsystem.rb:199:in `pxe_files' | /usr/share/foreman/app/models/concerns/orchestration/tftp.rb:111:in `setTFTPBootFiles' | /usr/share/foreman/app/models/concerns/orchestration.rb:222:in `execute' | /usr/share/foreman/app/models/concerns/orchestration.rb:145:in `block in process' | /usr/share/foreman/app/models/concerns/orchestration.rb:137:in `each' | /usr/share/foreman/app/models/concerns/orchestration.rb:137:in `process' | /usr/share/foreman/app/models/concerns/orchestration.rb:44:in `around_save_orchestration' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:136:in `run_callbacks' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:816:in `_run_save_callbacks' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/callbacks.rb:342:in `create_or_update' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/persistence.rb:275:in `save' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/validations.rb:46:in `save' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/transactions.rb:310:in `block (2 levels) in save' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/transactions.rb:387:in `block in with_transaction_returning_status' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/database_statements.rb:254:in `block in transaction' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/transaction.rb:239:in `block in within_new_transaction' | /opt/rh/rh-ruby25/root/usr/share/ruby/monitor.rb:226:in `mon_synchronize' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/transaction.rb:236:in `within_new_transaction' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/database_statements.rb:254:in `transaction' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/transactions.rb:212:in `transaction' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/transactions.rb:385:in `with_transaction_returning_status' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/transactions.rb:310:in `block in save' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/transactions.rb:325:in `rollback_active_record_state!' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/transactions.rb:309:in `save' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/suppressor.rb:44:in `save' | /usr/share/foreman/app/models/concerns/foreman/sti.rb:26:in `save' | /usr/share/foreman/app/controllers/hosts_controller.rb:104:in `create' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_controller/metal/basic_implicit_render.rb:6:in `send_action' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/abstract_controller/base.rb:194:in `process_action' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_controller/metal/rendering.rb:30:in `process_action' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/abstract_controller/callbacks.rb:42:in `block in process_action' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:109:in `block in run_callbacks' | /usr/share/foreman/app/controllers/concerns/application_shared.rb:15:in `set_timezone' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks' | /usr/share/foreman/app/models/concerns/foreman/thread_session.rb:32:in `clear_thread' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks' | /usr/share/foreman/app/controllers/concerns/foreman/controller/topbar_sweeper.rb:12:in `set_topbar_sweeper_controller' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks' | /opt/theforeman/tfm/root/usr/share/gems/gems/audited-4.7.1/lib/audited/sweeper.rb:14:in `around' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks' | /opt/theforeman/tfm/root/usr/share/gems/gems/audited-4.7.1/lib/audited/sweeper.rb:14:in `around' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:136:in `run_callbacks' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/abstract_controller/callbacks.rb:41:in `process_action' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_controller/metal/rescue.rb:22:in `process_action' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_controller/metal/instrumentation.rb:34:in `block in process_action' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/notifications.rb:168:in `block in instrument' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/notifications/instrumenter.rb:23:in `instrument' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/notifications.rb:168:in `instrument' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_controller/metal/instrumentation.rb:32:in `process_action' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_controller/metal/params_wrapper.rb:256:in `process_action' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/railties/controller_runtime.rb:24:in `process_action' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/abstract_controller/base.rb:134:in `process' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionview-5.2.1/lib/action_view/rendering.rb:32:in `process' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_controller/metal.rb:191:in `dispatch' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_controller/metal.rb:252:in `dispatch' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/routing/route_set.rb:52:in `dispatch' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/routing/route_set.rb:34:in `serve' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/journey/router.rb:52:in `block in serve' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/journey/router.rb:35:in `each' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/journey/router.rb:35:in `serve' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/routing/route_set.rb:840:in `call' | /opt/theforeman/tfm/root/usr/share/gems/gems/apipie-rails-0.5.9/lib/apipie/static_dispatcher.rb:65:in `call' | /opt/theforeman/tfm/root/usr/share/gems/gems/apipie-rails-0.5.9/lib/apipie/extractor/recorder.rb:136:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/middleware/static.rb:127:in `call' | /usr/share/foreman/lib/middleware/telemetry.rb:9:in `call' | /opt/theforeman/tfm/root/usr/share/gems/gems/apipie-rails-0.5.9/lib/apipie/middleware/checksum_in_headers.rb:27:in `call' | /usr/share/foreman/lib/middleware/catch_json_parse_errors.rb:8:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/tempfile_reaper.rb:15:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/etag.rb:25:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/conditional_get.rb:38:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/head.rb:12:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/http/content_security_policy.rb:18:in `call' | /usr/share/foreman/lib/middleware/logging_context.rb:23:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/session/abstract/id.rb:232:in `context' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/session/abstract/id.rb:226:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/middleware/cookies.rb:670:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/middleware/callbacks.rb:28:in `block in call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:98:in `run_callbacks' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/middleware/callbacks.rb:26:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/middleware/debug_exceptions.rb:61:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/middleware/show_exceptions.rb:33:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/railties-5.2.1/lib/rails/rack/logger.rb:38:in `call_app' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/railties-5.2.1/lib/rails/rack/logger.rb:28:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/sprockets-rails-3.2.1/lib/sprockets/rails/quiet_assets.rb:13:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/middleware/remote_ip.rb:81:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/middleware/request_id.rb:27:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/method_override.rb:22:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/runtime.rb:22:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activesupport-5.2.1/lib/active_support/cache/strategy/local_cache_middleware.rb:29:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/middleware/executor.rb:14:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/actionpack-5.2.1/lib/action_dispatch/middleware/static.rb:127:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/sendfile.rb:111:in `call' | /opt/theforeman/tfm/root/usr/share/gems/gems/secure_headers-6.0.0/lib/secure_headers/middleware.rb:13:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/railties-5.2.1/lib/rails/engine.rb:524:in `call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/railties-5.2.1/lib/rails/railtie.rb:190:in `public_send' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/railties-5.2.1/lib/rails/railtie.rb:190:in `method_missing' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/urlmap.rb:68:in `block in call' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/urlmap.rb:53:in `each' | /opt/theforeman/tfm-ror52/root/usr/share/gems/gems/rack-2.0.5/lib/rack/urlmap.rb:53:in `call'
--

This also happens when you try to use the default WAIK PXE.