missing setuptools
```
$ ./results/vcstool/bin/vcs --help
Traceback (most recent call last):
File "/nix/store/m9w0gapwnwffhnvyv3ds14mgbx2p5y93-vcstool-0.2.7/bin/.vcs-wrapped", line 6, in <module>
from vcstool.commands.vcs import main
File "/nix/store/m9w0gapwnwffhnvyv3ds14mgbx2p5y93-vcstool-0.2.7/lib/python3.7/site-packages/vcstool/commands/vcs.py", line 5, in <module>
from vcstool.commands.help import get_entrypoint
File "/nix/store/m9w0gapwnwffhnvyv3ds14mgbx2p5y93-vcstool-0.2.7/lib/python3.7/site-packages/vcstool/commands/help.py", line 6, in <module>
from pkg_resources import load_entry_point
ModuleNotFoundError: No module named 'pkg_resources'
```
cargo-asm hasn't seen any new releases since 2018 (and even then
it was spotty). But there have been improvements since then, so
switch to dated releases that use a working git commit.
Upgrades Hydra to the latest master/flake branch. To perform this
upgrade, it's needed to do a non-trivial db-migration which provides a
massive performance-improvement[1].
The basic ideas behind multi-step upgrades of services between NixOS versions
have been gathered already[2]. For further context it's recommended to
read this first.
Basically, the following steps are needed:
* Upgrade to a non-breaking version of Hydra with the db-changes
(columns are still nullable here). If `system.stateVersion` is set to
something older than 20.03, the package will be selected
automatically, otherwise `pkgs.hydra-migration` needs to be used.
* Run `hydra-backfill-ids` on the server.
* Deploy either `pkgs.hydra-unstable` (for Hydra master) or
`pkgs.hydra-flakes` (for flakes-support) to activate the optimization.
The steps are also documented in the release-notes and in the module
using `warnings`.
`pkgs.hydra` has been removed as latest Hydra doesn't compile with
`pkgs.nixStable` and to ensure a graceful migration using the newly
introduced packages.
To verify the approach, a simple vm-test has been added which verifies
the migration steps.
[1] https://github.com/NixOS/hydra/pull/711
[2] https://github.com/NixOS/nixpkgs/pull/82353#issuecomment-598269471
