remove stale dependency on "sure"

[a-detiste]

"sure" was a popular helper to "nose" ... a long time ago

[absurdfarce]

Good find @a-detiste! I've kicked off a Jenkins build just to confirm there aren't any unexpected regressions here but I'll be surprised if anything comes of it. Assuming there isn't a problem this should go in right away!

[absurdfarce]

Hey @a-detiste , unfortunately the Jenkins build detected a collection of new failures, most (or actually I think all?) in tests/integration/cqlengine/test_timestamp.py. That looks to be the only test that was using the "sure" module but apparently it was using it; when I run the integration test locally with your branch I get the following:

$ EVENT_LOOP_MANAGER="libev" CASSANDRA_VERSION="4.1.6" pytest -v tests/integration/cqlengine/test_timestamp.py

=========================================================================================== short test summary info ============================================================================================
FAILED tests/integration/cqlengine/test_timestamp.py::BatchTest::test_batch_is_included - AttributeError: 'str' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::CreateWithTimestampTest::test_batch - AttributeError: 'str' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::CreateWithTimestampTest::test_non_batch_syntax_integration - AttributeError: 'TestTimestampModel' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::CreateWithTimestampTest::test_non_batch_syntax_unit - AttributeError: 'str' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::CreateWithTimestampTest::test_non_batch_syntax_with_tll_integration - AttributeError: 'TestTimestampModel' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::CreateWithTimestampTest::test_non_batch_syntax_with_ttl_unit - AttributeError: 'str' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::CreateWithTimestampTest::test_timestamp_is_set_on_model_queryset - AttributeError: 'datetime.timedelta' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::CreateWithTimestampTest::test_timestamp_not_included_on_normal_create - AttributeError: 'str' object has no attribute 'shouldnt'
FAILED tests/integration/cqlengine/test_timestamp.py::UpdateWithTimestampTest::test_instance_update_in_batch - AttributeError: 'str' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::UpdateWithTimestampTest::test_instance_update_includes_timestamp_in_query - AttributeError: 'str' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::DeleteWithTimestampTest::test_blind_delete - AttributeError: 'TestTimestampModel' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::DeleteWithTimestampTest::test_blind_delete_with_datetime - AttributeError: 'TestTimestampModel' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::DeleteWithTimestampTest::test_delete_in_the_past - AttributeError: 'TestTimestampModel' object has no attribute 'should'
FAILED tests/integration/cqlengine/test_timestamp.py::DeleteWithTimestampTest::test_non_batch - AttributeError: 'TestTimestampModel' object has no attribute 'should'
====================================================================================== 14 failed, 124 warnings in 13.85s =======================================================================================

That "should" function appears to be part of the DSL provided by sure so if we're going to remove the dependency we'll need to replace all those usages with something else.

[a-detiste]

Indeed ... but it also means that nobody knows how sure works anymore.
Here's a new scaled-down PR for review.