We currently use the absolute path of these binaries in the
helper. This has some advantages but given that we control the
inputs for PATH in general it seems unnecessary.
We are also slightly inconsistent about this in the codebase but
favor the non absolute path version. A quick count:
```
$ git grep '"chroot"'|wc -l
13
$ git grep '"/usr/sbin/chroot"'|grep -v test_|wc -l
8
```
for `mount` and `umount` it seems this is the only place that uses
the absolute path.
It's not an important change but it has the nice property that it
allows us to use e.g. `testutil.mock_command()` in our tests and
it would be nice to be consistent.
- Add an extra call to `/bin/false` and explicitly set the `check`
argument for both `run()` calls.
- Compare full call_args_list. This checks that all the options are as
expected, that the `check` argument is set properly, and that the full
order of all the calls is as expected, including the chroot path.
Co-authored-by: Michael Vogt <michael.vogt@gmail.com>
For consistency, use subprocess.run() with check=True for the calls that
were previously using subprocess.check_call().
Update the affected tests to match.
Add a test for the chroot context that mocks subprocess.run() and
subprocess.check_call(). The test verifies that the functions are
called the expected number of times with the expected command (first
arg).
