Make numpy an optional dependency

[pshchelo]

The code in websocket.py is able to work without numpy being installed,
but numpy is specified as a hard dependency in setup.py.

This change moves numpy to extras_require section.
To install websockify with fast HyBi support, one should install it with

pip install websockify[fastHyBi]

to have numpy also automatically installed.

[jumpojoy]

I don't see any reason why we should install it permanently.

[DirectXMan12]

We have already discussed this some in #135 and #163. The conclusion that we've come to in the past is that most people will probably want the significant performance gain that comes with using numpy. It is technically currently possible to use websockify without numpy, but it's not recommended.

Can you provide the use case that requires you to not have numpy?

[pshchelo]

websockify is a dependency for several OpenStack components (Nova, Ironic). OpenStack project has massive CI that deploys these components from git source with pip and installs dependencies. Currently AFAIK we do not actually have tests that would benefit from numpy acceleration in websockify, and definitely not one every gate job that deploys Nova (which is the basic core component of OpenStack). Installing numpy from source currently takes about 4 minutes, and if we could shave those off on almost every run, this would be great improvement.

Thus I thought that having a choice to install an actually optional component is reasonable.

[DirectXMan12]

I'm hesitant to make numpy an optional dependency like that, since most users probably want the numpy acceleration (and I predict we'll get a lot of people who don't know why their new installs of websockify are suddenly slower).

Even though it's more hacky, I'd be more willing to implement a custom flag on the setup.py (which could be passed via a requirements.txt file as such: https://pip.pypa.io/en/latest/reference/pip_install/#per-requirement-overrides) that looked like --without-numpy-required or something like that (what is really needed is optional-with-default dependencies, but AFAIK there's no good way to do that).

I'm assuming that it's out of the question to just install a numpy from a distro package on the host system before the pip install command is run?

@kanaka, @samhed: what are your thoughts (I sympathize with @pshchelo WRT to the OpenStack build times ;-) )?

[samhed]

A flag for when you don't want numpy sounds good to me. I agree with @DirectXMan12 that the default behavior should be to use numpy.

[DirectXMan12]

Unfortunately, it looks like due to the way pip installs packages, the option I suggested above will not work (requirements are collected first into the egg-info, requirements are installed, and then the main setup.py install is called).

I'll see if I can find a solution, but I'm tempted to just say the solution here is to install numpy from a distro package, and then pip should be able to use that version. Alternatively you could potentially place websockify in its own requirements.txt file, and call pip with --no-deps on that.

[CendioOssman]

So close?