forbid protobuf 4.x for now
@@ -7,7 +7,7 @@ msgpack>=0.5.6
sortedcontainers
uvloop>=0.14.0
grpcio-tools>=1.33.2
-protobuf>=3.12.2
+protobuf>=3.12.2,<4.0.0
configargparse>=1.2.3
multiaddr>=0.0.9
pymultihash>=0.8.2
justheuristic