[Error] protoc object_detection/protos/*.proto --python_out=.

Install protobuf 3 on Ubuntu

# Make sure you grab the latest version 
curl -OL https://github.com/google/protobuf/releases/download/v3.2.0/protoc-3.2.0-linux-x86_64.zip 

# Unzip 
unzip protoc-3.2.0-linux-x86_64.zip -d protoc3 

# Move protoc to /usr/local/bin/ 
sudo mv protoc3/bin/* /usr/local/bin/ 

# Move protoc3/include to /usr/local/include/ 
sudo mv protoc3/include/* /usr/local/include/ 

# Optional: change owner 
sudo chown [user] /usr/local/bin/protoc 
sudo chown -R [user] /usr/local/include/google