Allows to run the tests on multiple operating systems and on the
infrastructure that the Cockpit team maintains.
`make vm` downloads one of Cockpit's test images (override which one
with TEST_OS) and installs rpms build from the local checkout of lorax.
The resulting image is placed in `test/images/$TEST_OS`.
TEST_OS can be set to any of Cockpit's supported images (default:
fedora-30).
Run `make check-vm` to run the CLI checks in the VM. The bulk of the
work is done in `test/check-cli`, which uses Cockpit's `bots` library to
start the VM and run the script in it.
Also included is a `test/run` script, which is the entrypoint for
Cockpit's test infrastructure.
Remove `except` block which immediately raises the same exception again (it's
not a subclass of another caught exception, so this is safe).
Remove a false positive, because it is not emitted from the code base.
Disable subprocess-popen-preexec-fn in startProgram, which is not used
internally.
