[AstroPy] IERS issue again

[E. Madison Bray]

Hi *Nicola

(Sorry, I'm in France, so same name different spelling)

On Sun, Nov 22, 2020 at 7:03 PM E. Madison Bray <erik.m.bray at gmail.com>
wrote:

> Hi Nicolas,
>
> Apologies for the late response. A few things:
>
> 1) I'm sorry you hate this particularly annoying problem.  It's especially
> prevalent on Windows, where Python itself ships some SSL root certificates
> to use to verify SSL resources on the internet.  Unfortunately if your
> Python installation is too old, the certificates it ships with might be
> expired.
>
> 2) It looks like you're using a very old version of Astropy, on Python
> 2.7, which is deprecated.  As soon as possible you should upgrade to Python
> 3; Python 3.7 is probably the most stable for most software you use, if not
> Python 3.8.
>
> 3) That said, you might be stuck on Python 2.7 for reasons I cannot know.
> And even if you were on a newer version of Python it might still be a
> problem.  This is a known issue in Astropy which has a fix at [1] which
> will be included in Astropy v4.3.0
>
> 4) There is a potential workaround, though mind you I have not tested it
> since I don't have Python 2.7 on Windows anymore.  The workaround is to use
> the certifi [2] package, which provides up-to-date SSL root certificates in
> a manner which is easy to use by Python [3].  Its source releases should
> still work on Python 2.7.  The next step is you need to "monkey patch" the
> `ssl` module of Python to ensure that it always uses the certificates from
> certifi.  Here's a way you can do that; you would run this in your script
> before trying to do anything with astropy.time:
>
> First you need to install certifi:
>
> ```
> > python2.7 -m pip install certifi
> ```
>
> Then in your Python code:
>
> ```
> import certifi
> import ssl
> orig_create_default_context = ssl.create_default_context
>
> def create_default_context(**kwargs):
>     kwargs['cafile'] = certifi.where()
>     return orig_create_default_context(**kwargs)
>
> ssl.create_default_context = create_default_context
> ```
>
> I believe this should work, but again I stress that it is untested.  Give
> it a try and see if it resolves the issue for you, and please report back
> here whether it works or not.
>
> Nevertheless I would encourage you to upgrade to Python 3 as soon as
> possible.
>
> Best,
> Madison
>
> [1] https://github.com/astropy/astropy/pull/10434
> [2] https://pypi.org/project/certifi/
>
> On Wed, Nov 18, 2020 at 7:26 PM Nicola Montecchiari <
> omega.centauri at gmail.com> wrote:
>
>> Hello everybody,
>>
>> after some months I am getting again an error while trying to connect to
>> the IERS.
>>
>> Python 2.7.18 (v2.7.18:8d21aa21f2, Apr 20 2020, 13:19:08) [MSC v.1500 32
>> bit (Intel)] on win32
>> astropy==2.0.16
>> numpy==1.16.6
>>
>> >>> from astropy.time import Time
>> >>> t = Time('2016:001')
>> >>> t.ut1
>> WARNING: failed to download
>> https://datacenter.iers.org/data/9/finals2000A.all and
>> ftp://cddis.gsfc.nasa.gov/pub/products/iers/finals2000A.all, using local
>> IERS-B: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify
>> failed (_ssl.c:727)>;<urlopen error ftp error: timed out>
>> [astropy.utils.iers.iers]
>> <Time object: scale='ut1' format='yday' value=2016:001:00:00:00.082>
>>
>> Is this a known issue?
>> Thanks a lot for your help
>> Nicola
>>
>>
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