Fix to work with current version of poltergeist. Don't recommend using.

gistfile1.rb

module Capybara::Poltergeist
  class Client
    def redirect_stdout
      prev_stdout = STDOUT.dup
      prev_stderror = STDERR.dup

      prev_stdout.autoclose = false
      $stdout = @write_io
      STDOUT.reopen(@write_io)

      prev_stderror.autoclose = false
      $stderr = @write_io
      STDERR.reopen(@write_io)

      yield
    ensure
      STDOUT.reopen(prev_stdout)
      $stdout = STDOUT
      STDERR.reopen(prev_stderror)
      $stderr = STDERR
    end
  end
end

class WarningSuppressor
  class << self
    def write(message)
      if message =~ /QFont::setPixelSize: Pixel size <= 0/ || message =~/CoreText performance note:/ then 0 else puts(message);1;end
    end
  end
end

Capybara.register_driver :poltergeist do |app|
  Capybara::Poltergeist::Driver.new(app, phantomjs_logger: WarningSuppressor)
end

Capybara.javascript_driver = :poltergeist