stdenv.mkDerivation: remove duplicate assertions

      ...

    }@attrs:

    # Policy on acceptable hash types in nixpkgs

    assert

      attrs ? outputHash

      -> (

        let

          algo = attrs.outputHashAlgo or (head (splitString "-" attrs.outputHash));

        in

        if algo == "md5" then throw "Rejected insecure ${algo} hash '${attrs.outputHash}'" else true

      );

    let

      # TODO(@oxij, @Ericson2314): This is here to keep the old semantics, remove when

      # no package has `doCheck = true`.