Djblets's packaging, and the world of Python packaging in general, has

gotten increasingly complex with time. Wheels are the preferred (and

better supported) format in the packaging world, and eggs are on their

way out. We also require a handful of node.js modules for static media

building.
This change adds significant improvements to our packaging setup, in

order to cover these issues and more.
setup.py is now driven almost entirely by metadata within the package.

It no longer lists dependencies, but rather makes use of a new

djblets.dependencies module, which lists all the npm and Python package

dependencies needed by Djblets. This allows for a couple of things.

Primarily, it allows us to consolidate all dependencies/version ranges

in one place. It also allows consumers of Djblets to refer to the same

versions for their own uses.
The setup.py develop command has been enhanced to install dependencies

via wheels. It does this by first ensuring we have a modern

pip/setuptools, and then invokes pip install -e ., which will perform

the equivalent of setup.py develop but with Wheels. (Behind the

scenes, it actually uses setup.py develop with shims to install the

wheel versions, so it's otherwise fully compatible.)
After that, it installs all the packages required for development (using

dev-requirements.txt), and then installs required modules from npm

(or npm-cache, if --use-npm-cache is installed).
The end result is that contributors to Djblets now only need to run

setup.py develop to have a fully working environment going.

Set up a brand new virtual environment and started fresh in the Djblets

source tree (no Djblets.egg-info, node_modules, dist, or build).
Ran ./setup.py develop. Saw that it upgraded setuptools and pip

and then installed the main package dependencies and development

dependencies. Following that, it installed the node.js modules.
Checked that all expected packages and files were installed. Successfully

ran all unit tests.