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, 15 insertions, 4 deletions

diff --git a/test/orm/test_events.py b/test/orm/test_events.py
index 37b4d0ae1..79b20e285 100644
--- a/test/orm/test_events.py
+++ b/test/orm/test_events.py
@@ -35,8 +35,10 @@ from sqlalchemy.orm import UserDefinedOption
 from sqlalchemy.sql.cache_key import NO_CACHE
 from sqlalchemy.testing import assert_raises
 from sqlalchemy.testing import assert_raises_message
+from sqlalchemy.testing import assert_warns_message
 from sqlalchemy.testing import AssertsCompiledSQL
 from sqlalchemy.testing import eq_
+from sqlalchemy.testing import expect_raises
 from sqlalchemy.testing import expect_warnings
 from sqlalchemy.testing import fixtures
 from sqlalchemy.testing import is_not
@@ -1059,7 +1061,7 @@ class MapperEventsTest(_RemoveListeners, _fixtures.FixtureTest):
         m1 = Mock()
 
         self.mapper_registry.map_imperatively(User, users)
-        assert_raises_message(
+        assert_warns_message(
             sa.exc.SAWarning,
             r"before_configured' and 'after_configured' ORM events only "
             r"invoke with the Mapper class as "
@@ -1070,7 +1072,7 @@ class MapperEventsTest(_RemoveListeners, _fixtures.FixtureTest):
             m1,
         )
 
-        assert_raises_message(
+        assert_warns_message(
             sa.exc.SAWarning,
             r"before_configured' and 'after_configured' ORM events only "
             r"invoke with the Mapper class as "
@@ -2197,7 +2199,12 @@ class SessionEventsTest(_RemoveListeners, _fixtures.FixtureTest):
 
         u2 = User(name="u1", id=1)
         sess.add(u2)
-        assert_raises(sa.exc.SAWarning, sess.commit)
+
+        with expect_raises(sa.exc.IntegrityError), expect_warnings(
+            "New instance"
+        ):
+            sess.commit()
+
         sess.rollback()
         eq_(
             canary,
@@ -2249,7 +2256,11 @@ class SessionEventsTest(_RemoveListeners, _fixtures.FixtureTest):
 
         u2 = User(name="u1", id=1)
         sess.add(u2)
-        assert_raises(sa.exc.SAWarning, sess.commit)
+        with expect_raises(sa.exc.IntegrityError), expect_warnings(
+            "New instance"
+        ):
+            sess.commit()
+
         sess.rollback()
         eq_(assertions, [True, True])