Build instructions for ethereumapis and python

script.sh

mkdir work
cd work

# Have the well known protos available somewhere on your system.
git clone git@github.com:googleapis/api-common-protos.git

# Have the ethereumapis repo somewhere on your system
git clone git@github.com:prysmaticlabs/ethereumapis.git

# Create some output directory
mkdir python_out

# From the working directory, you need to use the -I flags to indicate the well known protos repo
# and the ethereumAPIs repo. 
protoc -I=./ethereumapis -I=./api-common-protos/ --python_out=./python_out/ ./ethereumapis/eth/v1alpha1/beacon_chain.proto