Steps to Reproduce:
```
$ python
Python 3.5.3 (default, Dec 12 2020, 14:55:10)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pywikibot
>>> site = pywikibot.Site()
>>> text = 'iarchive:documentsofrussi027937mbp'
>>> link = pywikibot.Link(text, site, 0)
>>> link.title
```
(My code doesn't call `link.title` directly, but this is the shorter way to reproduce.)
Actual Results:
```
WARNING: Http response status 404
WARNING: Non-JSON response received from server iarchive:iarchive; the server may be down.
WARNING: Waiting 5.0 seconds before retrying.
WARNING: Http response status 404
WARNING: Non-JSON response received from server iarchive:iarchive; the server may be down.
WARNING: Waiting 10.0 seconds before retrying.
[...]
WARNING: Waiting 120.0 seconds before retrying.
WARNING: Http response status 404
WARNING: Non-JSON response received from server iarchive:iarchive; the server may be down.
```
Total time: ~32 minutes
Expected Results:
Better handle the fact that the target of an interwikilink may not be a wiki or that querying it will receive an acceptable response.