dont use exception catches for warnings; modernize xdist detection

Improvements to the test suite's integration with pytest such that the
"warnings" plugin, if manually enabled, will not interfere with the test
suite, such that third parties can enable the warnings plugin or make use
of the ``-W`` parameter and SQLAlchemy's test suite will continue to pass.
Additionally, modernized the detection of the "pytest-xdist" plugin so that
plugins can be globally disabled using PYTEST_DISABLE_PLUGIN_AUTOLOAD=1
without breaking the test suite if xdist were still installed. Warning
filters that promote deprecation warnings to errors are now localized to
SQLAlchemy-specific warnings, or within SQLAlchemy-specific sources for
general Python deprecation warnings, so that non-SQLAlchemy deprecation
warnings emitted from pytest plugins should also not impact the test suite.

Fixes: #7599
Change-Id: Ibcf09af25228d39ee5a943fda82d8a9302433726

1 files changed, 2 insertions, 1 deletions

diff --git a/test/orm/test_lazy_relations.py b/test/orm/test_lazy_relations.py
index ee6d53652..ed636ae42 100644
--- a/test/orm/test_lazy_relations.py
+++ b/test/orm/test_lazy_relations.py
@@ -25,6 +25,7 @@ from sqlalchemy.orm import relationship
 from sqlalchemy.orm import Session
 from sqlalchemy.orm import with_parent
 from sqlalchemy.testing import assert_raises
+from sqlalchemy.testing import assert_warns
 from sqlalchemy.testing import eq_
 from sqlalchemy.testing import fixtures
 from sqlalchemy.testing import is_
@@ -369,7 +370,7 @@ class LazyTest(_fixtures.FixtureTest):
         self.mapper_registry.map_imperatively(Order, orders)
         s = fixture_session()
         u1 = s.query(User).filter(User.id == 7).one()
-        assert_raises(sa.exc.SAWarning, getattr, u1, "order")
+        assert_warns(sa.exc.SAWarning, getattr, u1, "order")
 
     def test_callable_bind(self):
         Address, addresses, users, User = (