Numerous listers were using the same page_request method or equivalent
in their implementation so prefer to deduplicate that code by adding
an http_request method in base lister class: swh.lister.pattern.Lister.
That method simply wraps a call to requests.Session.request and logs
some useful info for debugging and error reporting, also an HTTPError
will be raised if a request ends up with an error.
All listers using that new method now benefit of requests retry when
an HTTP error occurs thanks to the use of the http_retry decorator.
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