我在Heroku上部署Rails应用程序，部署失败，并显示此错误消息。
Rails couldn't infer whether you are using multiple databases from your database.yml and can't generate the tasks for the non-primary databases. If you'd like to use this feature, please simplify your ERB.
我已经在Heroku上连续部署了一年多，没有做出任何重大改变。
更改涉及将gemfile从ruby"2.6.3"更新为ruby"3.1.2"。
这是全跟踪
Building on the Heroku-22 stack
Using buildpacks:
1. heroku/ruby
2. heroku/nodejs
Ruby app detected
Installing bundler 2.3.10
Removing BUNDLED WITH version in the Gemfile.lock
Compiling Ruby/Rails
###### WARNING:
Your app was upgraded to bundler 2.3.10.
Previously you had a successful deploy with bundler 2.2.21.
If you see problems related to the bundler version please refer to:
https://devcenter.heroku.com/articles/bundler-version#known-upgrade-issues
Using Ruby version: ruby-3.1.2
Purging Cache. Changing stack from heroku-18 to heroku-22
Installing dependencies using bundler 2.3.10
Running: BUNDLE_WITHOUT='development:test' BUNDLE_PATH=vendor/bundle BUNDLE_BIN=vendor/bundle/bin BUNDLE_DEPLOYMENT=1 bundle install -j4
A bunch of gems fetching and installing
Bundle complete! 22 Gemfile dependencies, 78 gems now installed.
Gems in the groups 'development' and 'test' were not installed.
Bundled gems are installed into `./vendor/bundle`
Post-install message from mailjet:
The Ruby wrapper for Mailjet has just been installed successfully, congrats!
Maybe you want to configure your credentials to use your account.
All informations available on https://github.com/mailjet/mailjet-gem.
But if you are using Rails, you'll be glad to generate it easily using:
$ rails generate mailjet:initializer
We hope you will enjoy Mailjet!
Bundle completed (86.70s)
Cleaning up the bundler cache.
Installing node-v16.13.1-linux-x64
Installing yarn-v1.22.17
Detecting rake tasks
Preparing app for Rails asset pipeline
Running: rake assets:precompile
Rails couldn't infer whether you are using multiple databases from your database.yml and can't generate the tasks for the non-primary databases. If you'd like to use this feature, please simplify your ERB.
rake aborted!
Psych::BadAlias: Unknown alias: default
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/webpacker-4.3.0/lib/webpacker/env.rb:30:in `available_environments'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/webpacker-4.3.0/lib/webpacker/env.rb:21:in `current'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/webpacker-4.3.0/lib/webpacker/env.rb:15:in `inquire'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/webpacker-4.3.0/lib/webpacker/env.rb:7:in `inquire'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/webpacker-4.3.0/lib/webpacker/instance.rb:11:in `env'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/webpacker-4.3.0/lib/webpacker/instance.rb:18:in `config'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/webpacker-4.3.0/lib/webpacker.rb:34:in `config'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/webpacker-4.3.0/lib/webpacker/railtie.rb:32:in `block in <class:Engine>'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/railties-6.0.5.1/lib/rails/initializable.rb:32:in `instance_exec'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/railties-6.0.5.1/lib/rails/initializable.rb:32:in `run'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/railties-6.0.5.1/lib/rails/initializable.rb:61:in `block in run_initializers'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/railties-6.0.5.1/lib/rails/initializable.rb:60:in `run_initializers'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/railties-6.0.5.1/lib/rails/application.rb:363:in `initialize!'
/tmp/build_f6d25fed/config/environment.rb:5:in `<main>'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.13.0/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:32:in `require'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.13.0/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:32:in `require'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/zeitwerk-2.6.0/lib/zeitwerk/kernel.rb:35:in `require'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/activesupport-6.0.5.1/lib/active_support/dependencies.rb:324:in `block in require'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/activesupport-6.0.5.1/lib/active_support/dependencies.rb:291:in `load_dependency'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/activesupport-6.0.5.1/lib/active_support/dependencies.rb:324:in `require'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/railties-6.0.5.1/lib/rails/application.rb:339:in `require_environment!'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/railties-6.0.5.1/lib/rails/application.rb:523:in `block in run_tasks_blocks'
/tmp/build_f6d25fed/vendor/bundle/ruby/3.1.0/gems/sprockets-rails-3.4.2/lib/sprockets/rails/task.rb:61:in `block (2 levels) in define'
Tasks: TOP => environment
(See full trace by running task with --trace)
!
! Precompiling assets failed.
!
! Push rejected, failed to compile Ruby app.
! Push failed
这是与新ruby版本的兼容性问题，只是添加了psych-gem就解决了这个问题。
gem 'psych', '< 4'