Code review comment for ~xiaofengw/cloud-init:xiaofengw-user-defined-script

> > One question about the unittest. I'm marking this WIP, when you've replied,
> > please change the state back to Needs Review.
> Thanks, please check my answer in line.
This is still needed. I removed this line and the test failed with "called subp. set allowed_subp=True to allow subp" error.
I checked the _fake_subp logic, it require to set allowed_subp to True if we call util.subp function no matter util.subp is mocked or not.