IERS data url is down and backup not used

[maxnoe]

The download URL for IERS data is down: http://maia.usno.navy.mil/ser7/finals2000A.all

however, there is a backup still working here: http://toshi.nofs.navy.mil/ser7/finals2000A.all

Would it be possible to add a solution that also trys the backup server like it is done for other downloads?

[pllim]

cc @taldcroft

[mhvk]

Might this also be why currently travis tests of iau_full_stack are stalling? If so, we definitely need to change those - at least, I thought that for our normal tests we do not download anything from outside of astropy.

[pllim]

(UPDATED)

IERS_B_URL is working and appears to be the default.

# by default for IERS class, read IERS-B table
IERS.read = IERS_B.read

But config is the opposite. 🤷‍♀️

    iers_auto_url = _config.ConfigItem(
        IERS_A_URL,
        'URL for auto-downloading IERS file data.')

[pllim]

Haha, @mhvk ! Incidentally, I marked that test as requiring remote data in #8033 (it is not correctly marked as so) but it is not merged yet. (UPDATE: I merged it.)

[mhvk]

Something that is also odd is that rather than just timing out, the whole testing machinery hangs.

[pllim]

I'll see if I can hack something quick for this since it appears to be affecting everything...

UPDATE: See #8308