canonical#343)

And raise TypeError when subp called with no args, which more accurately mirrors normal behaviour:

>>> from cloudinit.util import subp
>>> subp()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: subp() missing 1 required positional argument: 'args'

Create a schema object for the `apt_configure` module and
validate this schema in the `handle`  function of the module.

There are some considerations regarding this PR:

* The `primary` and `security` keys have the exact same properties. I
  tried to eliminate this redundancy by moving their properties to a
  common place and then just referencing it for both security and
  primary. Similar to what is documented here:
    https://json-schema.org/understanding-json-schema/structuring.html
  under the `Reuse` paragraph.  However, this approach does not work,
  because the `#` pointer goes to the beginning of the file, which is
  a python module instead of a json file, not allowing the pointer to
  find the correct definition. What I did was to create a separate dict
  for the mirror config and reuse it for primary and security, but
  maybe there are better approaches to do that.
* There was no documentation for the config `debconf_selections`. I
  tried to infer what it supposed to do by looking at the code and the
  `debconf-set-selections`  manpage, but my description may not be
  accurate or complete.
* Add a _parse_description function to schema.py to render multi-line
  preformatted content instead of squashing all whitespace

LP: #1858884

This ensures that Travis will not kill our tests if fetching images is
taking a long time.

In implementation terms, this introduces a context manager which will
spin up a multiprocessing.Process in the background and print a dot to
stdout every 10 seconds.  The process is terminated when the context
manager exits.

This also drop the use of travis_wait, which was being used to work
around this issue.

…l#361)

We live in the future now.

We recently discovered that pylint is failing to report some errors when
invoked across our entire codebase (see
pylint-dev/pylint#3611).  I've run pylint across
every Python file under cloudinit/[0], and this commit fixes the issues
so-discovered.

[0] find cloudinit/ -name "*.py" | xargs -n 1 -t .tox/pylint/bin/python -m pylint

…#368)

We are longer using lxd.readthedocs.io

Signed-off-by: Thomas Parrott thomas.parrott@canonical.com

and slower.
and since we're making it slower, let's cache it, in case boottime gets
called more than once.

Specifically, ensure that given values are either strings, or arrays of strings.