Move impala imports out of global namespace into tests where its used

Should IbisTestEnv be using impala when its doing file system testing?

In Ibis filesystems means actually hdfs, and hdfs is only supported with Impala afaik. I thought on moving it inside the backend, but it’s part of the public API, so users may be using it, so it requires more thought, discussion, and probably a deprecation warning first.

In any case, we should be calling pytest with not hdfs, and that should prevent test_filesystems from running. But I guess that import is in the global namespace, and that’s causing the issue. Not sure why this is just failing in this PR. If you want to move that import inside the test/tests where it’s being used (assuming it’s not too many) that would be good. Probably better in a separate PR.

Thanks for all the work with this @matthewmturner, really happy to have you fixing all this technical debt.

_Originally posted by @datapythonista in https://github.com/ibis-project/ibis/pull/2435#issuecomment-707612410_

[datapythonista]

Would the idea be to move the global ENV = IbisTestEnv() and from ibis.impala.tests.conftest import IbisTestEnv into an __init__ method for each of those classes with a variable like self.ENV = IbisTestEnv() and then update references to cls.ENV to self.ENV?

I think should be as easy as replacing this:

cls.ENV = ENV

By

from ibis.impala.tests.conftest import IbisTestEnv
cls.ENV = IbisTestEnv()

And then removing the import and the initialization of IbisTestEnv from the global namespace.

[matthewmturner]

closed via #2470