Install argparse package on lucid (package < v2.7)

Ubuntu lucid ships with the default python package that's 2.6.x, which doesn't come with argparse. This should do the trick, but untested:

```rb
case node['platform_family']
when "debian"
  if node['python']['install_method'] == "package" && node['platform'].to_i == 10
    python_pip "argparse"
  end
end
```

I'll submit a PR when I get a sec :)