@@ -38,7 +38,7 @@ module Selenium
         port
       end
 
-      IGNORED_ERRORS = [Errno::EADDRNOTAVAIL]
+      IGNORED_ERRORS = [Errno::EADDRNOTAVAIL].freeze
       IGNORED_ERRORS << Errno::EBADF if Platform.cygwin?
       IGNORED_ERRORS.freeze
 
# encoding: utf-8
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#
#   http://www.apache.org/licenses/LICENSE-2.0
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# under the License.

module Selenium
  module WebDriver
    class PortProber
      def self.above(port)
        port += 1 until free? port
        port
      end

      def self.random
        # TODO: Avoid this
        #
        # (a) should pick a port that's guaranteed to be free on all interfaces
        # (b) should pick a random port outside the ephemeral port range
        #
        server = TCPServer.new(Platform.localhost, 0)
        port   = server.addr[1]
        server.close

        port
      end

      IGNORED_ERRORS = [Errno::EADDRNOTAVAIL]
      IGNORED_ERRORS << Errno::EBADF if Platform.cygwin?
      IGNORED_ERRORS.freeze

      def self.free?(port)
        Platform.interfaces.each do |host|
          begin
            TCPServer.new(host, port).close
          rescue *IGNORED_ERRORS => ex
            WebDriver.logger.debug("port prober could not bind to #{host}:#{port} (#{ex.message})")
            # ignored - some machines appear unable to bind to some of their interfaces
          end
        end

        true
      rescue SocketError, Errno::EADDRINUSE
        false
      end
    end # PortProber
  end # WebDriver
end # Selenium

We can't freeze this and then add something to it in the next line. The `freeze` on line 43 is sufficient. If Rubocop flags this we need to exclude it.