fix to make Rails 4 work with Postgres gem > 0.20.0

application.rb

# fix to make Rails 4 work with Postgres gem > 0.20.0
#
# place this in your config/application.rb just after the Bundler.require() line
module Kernel
  def gem_with_pg_fix(dep, *reqs)
    if dep == "pg" && reqs == ["~> 0.15"]
      reqs = ["~> 1.0"]
    end
    gem_without_pg_fix(dep, *reqs)
  end

  alias_method_chain :gem, :pg_fix
end

PGconn   = PG::Connection
PGresult = PG::Result
PGError  = PG::Error

Thanks this was still helpful all these years later!