each_response_header

# File lib/net/http.rb, line 2032
      def each_response_header(sock)
        while true
          line = sock.readuntil("\n", true).sub(/\s+\z/, '')
          break if line.empty?
          m = /\A([^:]+):\s*/.match(line) or
              raise HTTPBadResponse, 'wrong header line format'
          yield m[1], m.post_match
        end
      end