# File lib/webmock/http_lib_adapters/net_http.rb, line 306
    def self.validate_headers(headers)
      # For Ruby versions < 2.3.0, if you make a request with headers that are symbols
      # Net::HTTP raises a NoMethodError
      #
      # WebMock normalizes headers when creating a RequestSignature,
      # and will update all headers from symbols to strings.
      #
      # This could create a false positive in a test suite with WebMock.
      #
      # So before this point, WebMock raises an ArgumentError if any of the headers are symbols
      # instead of the cryptic NoMethodError "undefined method `split' ...` from Net::HTTP
      if Gem::Version.new(RUBY_VERSION) < Gem::Version.new('2.3.0')
        header_as_symbol = headers.keys.find {|header| header.is_a? Symbol}
        if header_as_symbol
          raise ArgumentError.new("Net:HTTP does not accept headers as symbols")
        end
      end
    end