Since upgrade to 1.7.4, when I use facts as values in hashes, if hashes are merged the yaml generation for the node fails and I can't edit the node in Foreman.
In foreman logs (debug mode), I have the message :

Failed to generate external nodes for XXXXX.XXXXXX.XXXXX.XXXXX.fr with undefined method `each_pair' for #<String:0x00000001fdfdd0>
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/core_ext/hash/deep_merge.rb:15:in `deep_merge!'
/usr/share/foreman/app/services/classification/base.rb:199:in `block in update_hash_matcher'
/usr/share/foreman/app/services/classification/base.rb:194:in `each'
/usr/share/foreman/app/services/classification/base.rb:194:in `update_hash_matcher'
/usr/share/foreman/app/services/classification/base.rb:54:in `block in values_hash'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activerecord-3.2.21/lib/active_record/relation/delegation.rb:6:in `each'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activerecord-3.2.21/lib/active_record/relation/delegation.rb:6:in `each'
/usr/share/foreman/app/services/classification/base.rb:40:in `values_hash'
/usr/share/foreman/app/services/classification/class_param.rb:6:in `enc'
/usr/share/foreman/app/models/host/managed.rb:845:in `lookup_keys_class_params'
/usr/share/foreman/app/models/host/managed.rb:386:in `info'
/usr/share/foreman/app/controllers/hosts_controller.rb:172:in `block (2 levels) in externalNodes'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal/mime_responds.rb:196:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal/mime_responds.rb:196:in `respond_to'
/usr/share/foreman/app/controllers/hosts_controller.rb:170:in `externalNodes'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal/implicit_render.rb:4:in `send_action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/abstract_controller/base.rb:167:in `process_action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal/rendering.rb:10:in `process_action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/abstract_controller/callbacks.rb:18:in `block in process_action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:549:in `block (3 levels) in _run__1662959498352087448__process_action__946288385558330859__callbacks'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:215:in `block in _conditional_callback_around_7294'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:326:in `around'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:310:in `_callback_around_1843'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:214:in `_conditional_callback_around_7294'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:526:in `block (2 levels) in _run__1662959498352087448__process_action__946288385558330859__callbacks'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:215:in `block in _conditional_callback_around_7293'
/usr/share/foreman/app/models/concerns/foreman/thread_session.rb:33:in `clear_thread'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:214:in `_conditional_callback_around_7293'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:415:in `block in _run__1662959498352087448__process_action__946288385558330859__callbacks'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:215:in `block in _conditional_callback_around_7292'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:326:in `around'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:310:in `_callback_around_13'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:214:in `_conditional_callback_around_7292'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:403:in `_run__1662959498352087448__process_action__946288385558330859__callbacks'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:405:in `__run_callback'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:81:in `run_callbacks'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/abstract_controller/callbacks.rb:17:in `process_action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal/rescue.rb:29:in `process_action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/notifications.rb:123:in `block in instrument'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/notifications.rb:123:in `instrument'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal/instrumentation.rb:29:in `process_action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal/params_wrapper.rb:207:in `process_action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activerecord-3.2.21/lib/active_record/railties/controller_runtime.rb:18:in `process_action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/abstract_controller/base.rb:121:in `process'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/abstract_controller/rendering.rb:45:in `process'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal.rb:203:in `dispatch'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_controller/metal.rb:246:in `block in action'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/routing/route_set.rb:73:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/routing/route_set.rb:36:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/journey-1.0.4/lib/journey/router.rb:68:in `block in call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/journey-1.0.4/lib/journey/router.rb:56:in `each'
/usr/share/foreman/vendor/ruby/1.9.1/gems/journey-1.0.4/lib/journey/router.rb:56:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/routing/route_set.rb:608:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/apipie-rails-0.2.6/lib/apipie/static_dispatcher.rb:65:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/apipie-rails-0.2.6/lib/apipie/extractor/recorder.rb:97:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/apipie-rails-0.2.6/lib/apipie/middleware/checksum_in_headers.rb:27:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-1.4.5/lib/rack/etag.rb:23:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-1.4.5/lib/rack/conditionalget.rb:25:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/head.rb:14:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/params_parser.rb:21:in `call'
/usr/share/foreman/lib/middleware/catch_json_parse_errors.rb:9:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/flash.rb:242:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-1.4.5/lib/rack/session/abstract/id.rb:210:in `context'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-1.4.5/lib/rack/session/abstract/id.rb:205:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/cookies.rb:341:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activerecord-3.2.21/lib/active_record/query_cache.rb:64:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activerecord-3.2.21/lib/active_record/connection_adapters/abstract/connection_pool.rb:479:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:405:in `_run__2006362726624907426__call__2506133319130815461__callbacks'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:405:in `__run_callback'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/callbacks.rb:81:in `run_callbacks'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/callbacks.rb:27:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/railties-3.2.21/lib/rails/rack/logger.rb:32:in `call_app'
/usr/share/foreman/vendor/ruby/1.9.1/gems/railties-3.2.21/lib/rails/rack/logger.rb:16:in `block in call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/tagged_logging.rb:22:in `tagged'
/usr/share/foreman/vendor/ruby/1.9.1/gems/railties-3.2.21/lib/rails/rack/logger.rb:16:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/request_id.rb:22:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-1.4.5/lib/rack/methodoverride.rb:21:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-1.4.5/lib/rack/runtime.rb:17:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/activesupport-3.2.21/lib/active_support/cache/strategy/local_cache.rb:72:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/actionpack-3.2.21/lib/action_dispatch/middleware/static.rb:83:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-cache-1.2/lib/rack/cache/context.rb:136:in `forward'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-cache-1.2/lib/rack/cache/context.rb:245:in `fetch'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-cache-1.2/lib/rack/cache/context.rb:185:in `lookup'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-cache-1.2/lib/rack/cache/context.rb:66:in `call!'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-cache-1.2/lib/rack/cache/context.rb:51:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/railties-3.2.21/lib/rails/engine.rb:484:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/railties-3.2.21/lib/rails/application.rb:231:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/railties-3.2.21/lib/rails/railtie/configurable.rb:30:in `method_missing'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-1.4.5/lib/rack/builder.rb:134:in `call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-1.4.5/lib/rack/urlmap.rb:64:in `block in call'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-1.4.5/lib/rack/urlmap.rb:49:in `each'
/usr/share/foreman/vendor/ruby/1.9.1/gems/rack-1.4.5/lib/rack/urlmap.rb:49:in `call'
/usr/lib/ruby/vendor_ruby/phusion_passenger/rack/request_handler.rb:96:in `process_request'
/usr/lib/ruby/vendor_ruby/phusion_passenger/abstract_request_handler.rb:516:in `accept_and_process_next_request'
/usr/lib/ruby/vendor_ruby/phusion_passenger/abstract_request_handler.rb:274:in `main_loop'
/usr/lib/ruby/vendor_ruby/phusion_passenger/rack/application_spawner.rb:206:in `start_request_handler'
/usr/lib/ruby/vendor_ruby/phusion_passenger/rack/application_spawner.rb:171:in `block in handle_spawn_application'
/usr/lib/ruby/vendor_ruby/phusion_passenger/utils.rb:479:in `safe_fork'
/usr/lib/ruby/vendor_ruby/phusion_passenger/rack/application_spawner.rb:166:in `handle_spawn_application'
/usr/lib/ruby/vendor_ruby/phusion_passenger/abstract_server.rb:357:in `server_main_loop'
/usr/lib/ruby/vendor_ruby/phusion_passenger/abstract_server.rb:206:in `start_synchronously'
/usr/lib/ruby/vendor_ruby/phusion_passenger/abstract_server.rb:180:in `start'
/usr/lib/ruby/vendor_ruby/phusion_passenger/rack/application_spawner.rb:129:in `start'
/usr/lib/ruby/vendor_ruby/phusion_passenger/spawn_manager.rb:253:in `block (2 levels) in spawn_rack_application'
/usr/lib/ruby/vendor_ruby/phusion_passenger/abstract_server_collection.rb:132:in `lookup_or_add'
/usr/lib/ruby/vendor_ruby/phusion_passenger/spawn_manager.rb:246:in `block in spawn_rack_application'
/usr/lib/ruby/vendor_ruby/phusion_passenger/abstract_server_collection.rb:82:in `block in synchronize'
<internal:prelude>:10:in `synchronize'
/usr/lib/ruby/vendor_ruby/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'
/usr/lib/ruby/vendor_ruby/phusion_passenger/spawn_manager.rb:244:in `spawn_rack_application'
/usr/lib/ruby/vendor_ruby/phusion_passenger/spawn_manager.rb:137:in `spawn_application'
/usr/lib/ruby/vendor_ruby/phusion_passenger/spawn_manager.rb:275:in `handle_spawn_application'
/usr/lib/ruby/vendor_ruby/phusion_passenger/abstract_server.rb:357:in `server_main_loop'
/usr/lib/ruby/vendor_ruby/phusion_passenger/abstract_server.rb:206:in `start_synchronously'
/usr/share/phusion-passenger/helper-scripts/passenger-spawn-server:99:in `<main>'

For example, for my apt configuration, the "sources" smart variable is :

Matcher : osfamily=debian
Value :
puppetlabs:
  location: http://apt.puppetlabs.com/
  release: <%= @host.facts['lsbdistcodename'] %>
  repos: main dependencies
  include_src: false
Matcher : lsbdistcodename=wheezy
Value :
wheezy-updates:
  location: http://ftp.fr.debian.org/debian/
  release: wheezy-updates
  repos: main
  include_src: false
wheezy:
  location: http://ftp.fr.debian.org/debian/
  release: wheezy
  repos: main contrib non-free
wheezy-security:
  location: http://security.debian.org/
  release: wheezy/updates
  repos: main contrib non-free
  include_src: false