findstat error handling

[mantepse]

Raise appropriate errors when there are problems in the communication with findstat.org.

Moreover, add support for the new findstat collection "finite lattices".

Finally, we fix some pyflakes issues.

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​6d311b2

add doctest

[slelievre]

Use an url at example.com so nobody can play a trick? Check if that works.

-        sage: _get_json("https://nonexistingfindstaturl.org")
+        sage: _get_json("https://not-findstat.example.com")
         Traceback (most recent call last):
         ...
-        ConnectionError: HTTPSConnectionPool(host='nonexistingfindstaturl.org', port=443): Max retries exceeded with url: / (Caused by NewConnectionError('...Failed to establish a new connection: [Errno -2] Name or service not known'))
+        ConnectionError: HTTPSConnectionPool(host='not-findstat.example.com', port=443): Max retries exceeded with url: / (Caused by NewConnectionError('...Failed to establish a new connection: [Errno -2] Name or service not known'))

Don't forget to set to needs_review when ready.

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​8ab688c

better error handling and doctest

[mantepse]

It turns out that testing what I really want to test is tricky:

• I originally wanted to test that an error is raised when findstat is down.

• using badurl.example.com or the like does not test this, because the domain does not exist. In this case request also throws nested errors, which are hard to catch.

Therefore, I test something else, which makes more sense to test anyway.

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​12f0339

error handling also for post requests

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​a26e753

reenable support for unsupported collections, remove obsolete code

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​27476c5

add lattices to supported collections

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​3f89b5b

fix doctests, simplify iterator, fix missing import

[gh-kliem]

Can you please modify the ticket description so that you see that the support for new collections is added.

[vdelecroix]

Why are you turning the JSONDecodeError into a ValueError?

[mantepse]

Because the reason for the error is (most likely) an inappropriate value response.text, due to (most likely) a bad url or a new but on the findstat server. I felt that a ValueError would then be more correct.

For example, upon

sage: findstat()
The Combinatorial Statistic Finder (https://www.findstat.org/)
sage: sage.databases.findstat._get_json("https://www.findstat.org/")

if I only threw the JSONDecodeError, the message would simply be

JSONDecodeError: Expecting value: line 1 column 1 (char 0)

which wouldn't be helpful at all.

Thus I want to provide the response.text, which in this example would be the html of the frontpage of findstat. Seeing this, I would immediately know that I forgot api in the url, which is a ValueError, I think.

[slabbe]

green bot + works for me

[mantepse]

Thank you!