Merge pull request #10710 from senny/5554_let_the_database_raise_on_counts

Remove column restrictions for `#count`, let the database raise if the SQL is invalid.
Don't blindly call blame_file! on exceptions in ActiveSupport::Dependencies::Loadable

It is possible under some environments to receive an Exception that is
not extended with Blamable (e.g. JRuby).
ActiveSupport::Dependencies::Loadable#load_dependency blindly call
blame_file! on the exception which throws it's own NoMethodError
exception and hides the original Exception.

This commit fixes #9521
Merge pull request #10795 from atambo/master

Don't blindly call blame_file! on exceptions in ActiveSupport::Dependes::Loadable
fix ActiveModel::Validations.validators_on doc
Merge pull request #10906 from darai2k/fix-activemodel-validations-doc

fix ActiveModel::Validations.validators_on doc
fixture setup does not rely on `AR::Base.configurations`.

As you can also configure your database connection using `ENV["DATABASE_URL"]`,
the fixture setup can't reply on the `.configurations` Hash.

As the fixtures are only loaded when ActiveRecord is actually used
(`rails/test_help.rb`) it should be safe to drop the check for an existing configuration.