This is an alternative approach to solve the problem identified
in #279 . When doing API calls with `retry_on_error` set to
true (the default), if the call fails after all retries are
exhausted, we raise our own `MaximumRetriesExceeded` exception,
which tells you nothing about what actually went wrong, just
that we exhausted the retry count. It seems much more useful
to raise an exception with information about why the connection
is failing.

This changes that behaviour so that, on most paths, we would
raise an appropriate exception from requests (either the one
we caught, or an HTTPError via `raise_for_status`) if we exhaust
the retry count. Only if we fail due to database lag would we
still raise `MaximumRetriesExceeded` (because there isn't really
an underlying exception we can handily raise in that case).

Note that it was already possible to hit
`stream.raise_for_status()` before this change, if the status
code was outside the 500 range, so in theory callers should
already be prepared for that. It was not possible to get a
`requests.exceptions.ConnectionError` or
`requests.exceptions.Timeout` with `retry_on_error` true, though,
so this is genuinely a behaviour change on that front.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

Issue #290 gives an example of a wiki with protected pages whose
protection definitions have no 'expiry' key at all. This seems
strange and, on a quick through the mediawiki code, difficult
to achieve, but since there's a live site out there that does it,
and mediawiki *does* seem to have at least some code to handle
such cases (e.g. how the expiry shows as 'indefinite' in the
page information), let's handle it too, by representing this as
None.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

It seems that pytest-cov does not collect any coverage without
this file.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

`clientlogin()` does `self.require(1, 27)`, which needs the site
instance's `version` attribute to be set, but this is usually
done by `site_init()`, which is mocked out in the tests. We can
fix the problem by just manually setting a sufficiently high
version in the tests.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

Allow specifying `uselang` with `Page.revisions()` and
`Site.usercontributions()` to get localized parsed comments with
`prop=parsedcomment`.

Breaking change: Change the `Site.ask()` method to produce less nested
output. Basically, change `yield {title: answer}` to `yield answer`. The
title is included in the answer object after all.

The rvexpandtemplates parameter has been removed, but we can use
action=expandtemplates instead.

This fixes tests not being added to the source package.