Fixes https://github.com/m-labs/artiq-comtools/issues/7.
Basically, python subprocesses can't see all installed python packages
in a python environment because it uses the wrong Python exe (i.e. it
doesn't use the wrapped exe). This patches the PATH in the binary
wrappers (e.g. */bin/artiq_session) to include the correct python path.
Changes "name = '...-${version}" -> "pname = '...'" syntax everywhere
that is easy.
This matches current best nixpkgs convention.
The nixpkgs standard derivation will convert this to name =
"${pname}-${version}" automatically.
This also has the added benefit of adding the version to the filepath
for several packages that didn't have it before.
The only remaining files are ./artiq-full/extras.nix &
./artiq-fast/pkgs/python-deps.nix.
extras.nix had a
semi-confusing function that I didn't want to mess with.
