|          ^^^^^^^ a collection of type `std::vec::Vec<std::boxed::Box<futures::Future<Item=bazel_protos::remote_execution::DirectoryNode, Error=std::string::String>>>` cannot be built from an iterator over elements of type `std::boxed::Box<futures_cpupool::CpuFuture<bazel_protos::remote_execution::DirectoryNode, std::string::String>>`
    |
    = help: the trait `std::iter::FromIterator<std::boxed::Box<futures_cpupool::CpuFuture<bazel_protos::remote_execution::DirectoryNode, std::string::String>>>` is not implemented for `std::vec::Vec<std::boxed::Box<futures::Future<Item=bazel_protos::remote_execution::DirectoryNode, Error=std::string::String>>>`