When authenticating again a registry, if the www-authenticate header
doesn't specify a service, exclude it from the url
Signed-off-by: harishsurf <hgovinda@redhat.com>
Co-authored-by: harishsurf <hgovinda@redhat.com>
requests will either throw a RequestException or a ConnectionError if it
fails to request the given url for whatever reason.
callers are only expected to treat UpstreamRegistryError, so we throw it
instead of the requests related exceptions, adding the original message
to the new exception.
introduces the possibility to pull images from external registries
through Quay, storing them locally for faster subsequent pulls.
Closes PROJQUAY-3030 and PROJQUAY-3033
