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.
Fix up 2to3 complaints. I've decided to do with wrapping list
comprehension inside list() to get the generators to run in several
places instead of list(map( or list(filter( which seem less readable to
me.
