copying torch/autograd/_functions/blas.py -> build/lib.linux-x86_64-3.6/torch/autograd/_functions

We also noted earlier that we could pass files and directories to the package_data keyword argument to the main setup() function, and that Setuptools would handle copying those files to the installation location. During build_py, these files are copied to the build/ directory, so we also see lines like:
copying torch/lib/libTH.so.1 -> build/lib.linux-x86_64-3.6/torch/lib
...
copying torch/lib/include/THC/generic/THCTensor.h -> build/lib.linux-x86_64-3.6/torch/lib/include/THC/generic

Building the Extension Modules
Finally, we need to build the Extension Modules, i.e. the PyTorch modules written in C++ using the CPython backend. This also constitutes the majority of the code logic in setup.py. Our overridden build_ext Command has some special logic before the extensions themselves are actually built:
```python
from tools.cwrap import cwrap