Why is my rails server issuing deprecation warning and not connection to sqlite3?

Question

I am starting rails by following this tutorial: http://ruby.railstutorial.org/ruby-on-rails-tutorial-book#sec-the_first_application which seems very nice.

At the beginning, the author talks about the importance of the versions for the gems and softwares, so I did my best to keep using the exact same versions.

I followed the tutorial and it all ran nicely, the installation was ok (from his suggested source: http://railsinstaller.org/en )I downloaded ruby 1.9.

After installing, I used rails new first_app to create my app, changed the Gemfile to this one:

source 'https://rubygems.org'
ruby '1.9.3' #In the tutorial is 2.0.0, but changed to match my ruby version, 
             #as specified in the tutorial
#ruby-gemset=railstutorial_rails_4_0

gem 'rails', '4.0.1'

group :development do
  gem 'sqlite3', '1.3.8'
end

gem 'sass-rails', '4.0.1'
gem 'uglifier', '2.1.1'
gem 'coffee-rails', '4.0.1'
gem 'jquery-rails', '3.0.4'
gem 'turbolinks', '1.1.1'
gem 'jbuilder', '1.0.2'

group :doc do
  gem 'sdoc', '0.3.20', require: false
end

When I run rails server command, I get the following error:

    DEPRECATION WARNING: config.whiny_nils option is deprecated and no longer works.
 (called from block in <top (required)> at D:/rails/first_app/config/environment
s/development.rb:10)
config.eager_load is set to nil. Please update your config/environments/*.rb fil
es accordingly:

  * development - set it to false
  * test - set it to false (unless you use a tool that preloads your test enviro
nment)
  * production - set it to true

But opening localhost:3000 works fine. Clicking on "About your application’s environment" link, generates an error

ActiveRecord::ConnectionNotEstablished

Rails.root: D:/rails/first_app

I checked and my database.yml is using sqlite3.

When I run rake db:create inside my app's folder, I get

rake aborted! Specified 'postgresql' for database adapter, but the gem is not loaded. Add gem 'pg' to your Gemfile.

I think that maybe these three issues are connected and the source of the problem is that error message when starting the rails server. What can I do to fix it, could it be the ruby version 1.9.3 instead of 2.0.0?

thanks!

EDIT: On this link, I found the solution for my issue on the whiny_nils deprecation

Rails 4 removed the whiny_nils feature. Read more about it in the ActiveRecord chapter.

To solve the deprecation warning, simply remove any lines that set config.whiny_nils. Rails 3 added the configuration by default in config/environments/development.rb and config/environments/test.rb by default.

No idea why creating an app and starting it with the same version would cause this problem, but ok. No.1 fixed :)

Edit2: In the same link, I fixed the config.eager_load issue by creating this config in my config files and setting a value.

The active record issue remains.

EDIT 3: This is my database.yml file

# SQLite version 3.x
#   gem install sqlite3
#
#   Ensure the SQLite 3 gem is defined in your Gemfile
#   gem 'sqlite3'
development:
  adapter: sqlite3
  database: db/development.sqlite3
  pool: 5
  timeout: 5000

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  adapter: sqlite3
  database: db/test.sqlite3
  pool: 5
  timeout: 5000

production:
  adapter: sqlite3
  database: db/production.sqlite3
  pool: 5
  timeout: 5000

Answer 1

Solved: I had a database_url pointing to a postgres DB in my system environment variables. I've done that when following an heroku tutorial long ago. I removed it and now it works fine.

Answer 2

I suggest a solution that I believe will work better for you:

Remove the version numbers from all of the gems other than rails

It will do rails 4 and ruby 2.0 and for you ruby 2.0 will probably work. If necessary have the ruby version as 1.9.3

This would probably work better for you now and in the future.
It's better to avoid all those specific version numbers for other gems to avoid having.... the version problems you are experiencing. You want to spend less time on that and more time on the actual app, rails code, ruby code, etc. Most gems can figure out the right versions and dependencies themselves.

Try quickly doing another app this way (make sure you "cd .." out of this app first before issuing that rails new command again). You'll also see that doing a new app is a surprisingly frequent thing when compared to some other, older frameworks.