Internal server error

Passenger encountered the following error:

The application spawner server exited unexpectedly

Exception class:
Passenger::Railz::ApplicationSpawner::Error
Backtrace:
# File Line Location
0 /dh/passenger/lib/passenger/railz/application_spawner.rb 109 in `spawn_application'
1 /dh/passenger/lib/passenger/spawn_manager.rb 228 in `spawn_rails_application'
2 /dh/passenger/lib/passenger/spawn_manager.rb 213 in `synchronize'
3 /dh/passenger/lib/passenger/spawn_manager.rb 213 in `spawn_rails_application'
4 /dh/passenger/lib/passenger/spawn_manager.rb 122 in `spawn_application'
5 /dh/passenger/lib/passenger/spawn_manager.rb 247 in `handle_spawn_application'
6 /dh/passenger/lib/passenger/abstract_server.rb 317 in `__send__'
7 /dh/passenger/lib/passenger/abstract_server.rb 317 in `main_loop'
8 /dh/passenger/lib/passenger/abstract_server.rb 168 in `start_synchronously'
9 /dh/passenger/bin/passenger-spawn-server 46