Arch Linux

Description:
Packages `cockpit-machines` and `cockpit-packagekit` miss a dependency for package `which`.

The tool which is required by package `cockpit-machines` to be able to add VMs. If package `which` is not installed, Cockpit will report that package `virt-install` needs to be installed (even if it is installed).

The tool which is required by package `cockpit-packagekit` to be able to open the relevant UI page. If package `which` is not installed, the browser reports:
```
Tracer failed: "{"problem":null,"exit_status":127,"exit_signal":null,"message":"--: line 1: which: command not found\n--: line 1: exec: import json\nfrom tracer.query import Query\n\nq = Query()\napplications = q.affected_applications().get()\n\n\ndef filter_by_type(apps, type_str):\n return [app.name for app in apps if app.type == type_str]\n\n\ndump_obj = {}\n# ignore type \"session\" for cockpit use case\ndump_obj[\"reboot\"] = filter_by_type(applications, \"static\")\ndump_obj[\"daemons\"] = filter_by_type(applications, \"daemon\")\ndump_obj[\"manual\"] = filter_by_type(applications, \"application\")\n\nprint(json.dumps(dump_obj))\n: not found"}", data: """"
```

The tool which might be needed by other package Cockpit packages or by Cockpit itself, but I haven't tested enough to determine

Additional info:
* package version(s): cockpit:286.1-1, cockpit-machines:285-1, cockpit-packagekit:286.1-1
* config and/or log files etc.
* link to upstream bug report, if any

Steps to reproduce:
Install `cockpit`, `cockpit-machines` and `cockpit-packagekit`.
Ensure `which` is not installed.

Visit in Cockpit the Virtual Machine page, and try to add a VM.
Visit in Cockpit the Applications page, and note that it fails to load.