../src/arrow/flight/server.cc:63:11: error: redefinition of 'pb' as an alias for a different namespace
namespace pb = arrow::flight::protocol;
          ^
/Users/uwe/mambaforge/conda-bld/arrow-cpp-ext_1613940663852/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehol/include/google/protobuf/port.h:44:11: note: previously defined as an alias for 'protobuf_future_namespace_placeholder'
namespace pb = ::protobuf_future_namespace_placeholder;
          ^
1 error generated.