Allow to skip test cases that download data

[mbanck]

Some build environments (like Ubuntu autobuilders) have internet firewalled off to ensure that the build process is self-contained. In cases like this, quite a few test cases seem to fail because they try to download stuff.

So it would be convenient if there was an option or switch to skip those tests.

[loriab]

I suppose that'll be the pubchem tests. Should be easy enough.

[mbanck]

whoa, do you ever sleep?? I've made the Debian such that it ignores test failures for now but sure would be nice to be able to run tests cleanly.

[dgasmith]

New testing decorator of:

import socket

def internet_connection():
    try:
        socket.create_connection(("www.google.com", 80))
        return True
    except OSError:
        return False

using_web = pytest.mark.skipif(internet_connection() is False, reason="Could not connect to the internet")

@loriab Can you grab this? Currently my dev env is in a fragile state trying to propagate the Array changes.

[mbanck]

sorry, I never tested that back then; I've now checked that the pytests pass fine on my notebook (once I install certifi), but on the Debian autobuilders (which disable networking) they still fail:

https://buildd.debian.org/status/fetch.php?pkg=qcelemental&arch=all&ver=0.17.0%2Bdfsg-2&stamp=1610282048&raw=0

E.g.:

>               raise URLError(err)
E               urllib.error.URLError: <urlopen error [Errno 111] Connection refused>

/usr/lib/python3.9/urllib/request.py:1345: URLError

Is this expected, or have there been some regressions since a4ebcca got committed?