Gem:: LoadError: ne peut pas activer pg (~> 0.18), déjà activé pg-1.0.0 [dupliquer]

cette question a déjà une réponse ici:

• application Rails Utilisant Adaptateur Postgres ne peut pas activer pg 1 réponse

j'ai fait les Rails tutoriel trouvé ici et ont réussi jusqu'à devoir migrer les commentaires migration utilisant $ rails db: migrate . Avant ce point, j'ai été en mesure de générer le modèle D'Article et migrer les Articles créer la migration sans problèmes. Entre ces deux migrations, rien n'a changé dans mon fichier Gemfile, donc je ne suis pas sûr que ce soit Bundler qui ait un problème.

Voici les erreurs, suivies de la sortie complète de la ligne de commande, ainsi que mon fichier Gemfile et schéma.rb:

Gem::LoadError: can't activate pg (~> 0.18), already activated pg-1.0.0.

Gem::LoadError: Specified 'postgresql' for database adapter, but the gem is not loaded. Add `gem 'pg'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).

Pleine sortie de ligne de commande

xxx:gangelo: ~/dev/rails/test/blog (master*) ☠  rbenv exec rails db:migrate
rails aborted!
Gem::LoadError: Specified 'postgresql' for database adapter, but the gem is not loaded. Add `gem 'pg'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:188:in `rescue in spec'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:185:in `spec'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:880:in `establish_connection'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_handling.rb:58:in `establish_connection'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:124:in `block (2 levels) in <class:Railtie>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `instance_eval'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `block in execute_hook'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:60:in `with_execution_control'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:65:in `execute_hook'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:50:in `block in run_load_hooks'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `each'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `run_load_hooks'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:326:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:25:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:6:in `<class:MySQLDatabaseTasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:3:in `<module:Tasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:2:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:1:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:74:in `<module:DatabaseTasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:35:in `<module:Tasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:2:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:1:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:34:in `block (3 levels) in <class:Railtie>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:21:in `block in perform'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:18:in `perform'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/command.rb:46:in `invoke'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands.rb:16:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/bin/rails:9:in `require'
/Users/gangelo/dev/rails/test/blog/bin/rails:9:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `load'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `call'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client.rb:30:in `run'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/bin/spring:49:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `load'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'

Caused by:
Gem::LoadError: can't activate pg (~> 0.18), already activated pg-1.0.0. Make sure all dependencies are added to Gemfile.
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/postgresql_adapter.rb:2:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:186:in `spec'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:880:in `establish_connection'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_handling.rb:58:in `establish_connection'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:124:in `block (2 levels) in <class:Railtie>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `instance_eval'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `block in execute_hook'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:60:in `with_execution_control'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:65:in `execute_hook'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:50:in `block in run_load_hooks'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `each'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `run_load_hooks'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:326:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:25:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:6:in `<class:MySQLDatabaseTasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:3:in `<module:Tasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:2:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:1:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:74:in `<module:DatabaseTasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:35:in `<module:Tasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:2:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:1:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:34:in `block (3 levels) in <class:Railtie>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:21:in `block in perform'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:18:in `perform'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/command.rb:46:in `invoke'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands.rb:16:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/bin/rails:9:in `require'
/Users/gangelo/dev/rails/test/blog/bin/rails:9:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `load'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `call'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client.rb:30:in `run'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/bin/spring:49:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `load'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'
Tasks: TOP => db:migrate => db:load_config
(See full trace by running task with --trace)

Gemfile

source 'https://rubygems.org'

ruby '2.3.1'

git_source(:github) do |repo_name|
  repo_name = "#{repo_name}/#{repo_name}" unless repo_name.include?("/")
  "https://github.com/#{repo_name}.git"
end


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.1.4'

# Use sqlite3 as the database for Active Record
# gem 'sqlite3'

# Use postgres as the database for Active Record
gem 'pg'

# Use Puma as the app server
gem 'puma', '~> 3.7'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.2'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '~> 5'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 3.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara', '~> 2.13'
  gem 'selenium-webdriver'
end

# gma - start
group :development, :test do
  gem 'rspec-rails', '~> 3.5', '>= 3.5.2'
  gem 'rspec-activemodel-mocks', '~> 1.0', '>= 1.0.3'
  gem 'shoulda-matchers', '~> 3.1', '>= 3.1.1'
  gem 'factory_bot_rails', '~> 4.8', '>= 4.8.2'
  gem 'ffaker', '~> 2.2'
  # gem 'timecop', '~> 0.8.1'
end
# gma - end

group :development do
  # Access an IRB console on exception pages or by using <%= console %> anywhere in the code.
  gem 'web-console', '>= 3.3.0'
  gem 'listen', '>= 3.0.5', '< 3.2'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
  gem 'spring-watcher-listen', '~> 2.0.0'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

Schema.rb

ActiveRecord::Schema.define(version: 20180110153949) do
  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"

  create_table "articles", force: :cascade do |t|
    t.string "title"
    t.text "text"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end
end

fichier de Migration

class CreateComments < ActiveRecord::Migration[5.1]
  def change
    create_table :comments do |t|
      t.string :commenter
      t.text :body
      t.references :article, foreign_key: true

      t.timestamps
    end
  end
end