error[E0432]: unresolved import `protobuf::code_writer`
  --> src/codegen.rs:40:15
   |
40 | use protobuf::code_writer::CodeWriter;
   |               ^^^^^^^^^^^ Could not find `code_writer` in `protobuf`
error: aborting due to previous error
error: failed to compile `grpcio-compiler v0.2.0`, intermediate artifacts can be found at `/tmp/cargo-install.yapt22UA3XVj`