Capris is a DSL for building programs that leverage the subprocess interface, licensed under the MIT license.
A taste of what using Capris looks like for bulding a simple git wrapper, along with all the unix utilities that you know and love:
>>> from capris import Command
>>> git, grep = Command('git'), Command('grep')
>>> pipe = git.log(n=10, pretty="oneline") | grep(r'[a-f0-9]\{40\}', o=None)
>>> str(pipe)
'git log -n 10 --pretty=oneline | grep -o [a-f0-9]\{40\}'
>>> response = pipe.run()
>>> response.status_code
0
>>> print response.std_out
...