Detect python 2 automatically
Detect python 2 automatically

This avoids having to change the script when on a machine that
supports both python 2 and python 3

jskeet/google-api-dotnet-client,jskeet/google-api-dotnet-client,googleapis/google-api-dotnet-client,googleapis/google-api-dotnet-client,jskeet/google-api-dotnet-client,googleapis/google-api-dotnet-client