Closes netork#110.
The seven failures had two causes, neither of them in the driver.
The `driver` fixture builds a LinuxDriver with `__new__`, bypassing `__init__`,
and never set `_sudo_password`. Every call through `_sudo()` therefore raised
AttributeError, which the callers' broad `except Exception` reported as
`{"success": False}` — so six apply_updates tests failed for a reason unrelated
to what they were asserting.
`test_apply_updates_apt_all_packages` had a second one: its `capture_send(cmd)`
double accepted no keyword arguments, while `_sudo()` passes `read_timeout`.
The seventh, the apt update listing test, supplied `side_effect=["",
APT_UPGRADABLE]` — two values for a cache refresh that never existed.
`_get_updates_apt` has made exactly one `_send` call since it was written in
2712389, so the empty first value was consumed and parsed as the package list.
Checked out that commit and ran it: the test failed there too. It was committed
red and never passed.
That settles the open question in netork#110: the implementation was not changed,
the tests were written against one that never existed. `get_available_updates`
reads the local apt cache deliberately — refreshing it needs sudo and would cost
a round trip on every poll — so there is no stale-cache bug behind the
`updates_available` warning.
Christian Manivong
ce40299033