incompatible with 'typing' module in py 3.7.x

[zhaoyanpeng]

ImportError: cannot import 'CallableMeta' and 'GenericMeta' from 'typing'. See line 2 in allennlp/allennlp/semparse/domain_languages/domain_language.py.

Reason: typing module in 3.7.x deprecated 'CallableMeta' and 'GenericMeta'.

[matt-gardner]

Ack, I'll look into this, thanks for letting me know. I thought our CI was running on python 3.7, but I guess not.

[schmmd]

@matt-gardner until recently we were using an old version of Python 3.6 (see #2298). I asked @joelgrus whether we should upgrade to 3.7 but he emphasized that most people are still on 3.6. Perhaps we should test each?

[matt-gardner]

Our CI already takes quite a long time; I wouldn't recommend duplicating it for python 3.7. I'm not sure what the right thing to do for CI is - maybe we could just run CI on 3.7? But then we run the risk of using 3.7-specific features and losing support for 3.6... I don't know.

[joelgrus]

we could add a 3.7 step that runs for master commits, then we'd know soon-ish if we broke 3.7 but not have to check it with every commit.

alternatively, we could have a bunch of "once a week" checks (e.g. the models on the website) that don't stop us from committing but at least alert us when things are subtlely wrong (and that we can check before we release)