Add scipy as a dependency to setup.py

[willfrey]

scipy is imported in both the torchvision.datasets.svhn module and the torchvision.models.inception module.

Alternatively, we could put this under extras_require and make the user explicitly request to install scipy as an additional dependency.

[fmassa]

scipy is an optiional dependency of torchvision, and is not required in most cases (that's why it's imported inside the function.

Is there a way to make it optional in the installation process?

[willfrey]

I've made the change to make it optional.

Just my two cents but I'd argue that importing it within a function and not having a graceful/seamless experience for the client means that it's very much a dependency. Having to just "know" that you need scipy for two particular methods isn't the nicest!

[fmassa]

Thanks!

[fmassa]

So, this is kind of debatable.

I've myself never used any of the modules that require scipy.
Also, PyTorch up until very recently didn't have a dependency on numpy either, it was optional.

But thanks for the PR!

[willfrey]

In my opinion, it's nice to have the dependency explicitly written at least somewhere in the setup.py file, where folks are most likely to look first.

Thanks for merging!