This change includes a few things:
1) Prefer python2 and pip2 when on the PATH, over the undecorated
names python and pip. This is the standard convention for package
managers like Pip, etc., to support Python2 and Python3 side-by-side.
2) Fail-fast if neither can be found on the PATH.
3) Check the reported version number for python, pip, and pylint, and
fail-fast if it doesn't report back 2.7, just to safeguard against
undecorated binaries with unsupported versions.
Also, we had not listed wheel as a dependency in the requirements.txt
file. This needs to be there to support building bdist_wheels. Fixed.
Our scripts currently copy the package.json that does *not* have
the expanded semver, so its version is simply "${VERSION}", and NPM
is very much not happy with that. We can just stop copying the
package.json explicitly since it's inside of the bin/ directory.
To install a package, we copied the pacakge to the destination root,
deleted the node_modules folder and then restored just the production
dependencies. Because of how we were using yarn, this meant hitting
the network, which sucks.
Make two changes:
1. Copy over the yarn.lock file we created when we did our initial
restore (e.g from `make ensure`) so yarn can reuse it.
2. Pass --offline to yarn when we do yarn install. Since we already
installed the packages previously (as part of `make ensure`) they will
be present in the cache and hence we do not need network access.
This cuts the time spent in the make install step by half or more.
