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, 7 insertions, 12 deletions

diff --git a/lib/sqlalchemy/testing/plugin/pytestplugin.py b/lib/sqlalchemy/testing/plugin/pytestplugin.py
index 7a62ad008..2ae6730bb 100644
--- a/lib/sqlalchemy/testing/plugin/pytestplugin.py
+++ b/lib/sqlalchemy/testing/plugin/pytestplugin.py
@@ -13,16 +13,10 @@ import itertools
 import operator
 import os
 import re
+import uuid
 
 import pytest
 
-try:
-    import xdist  # noqa
-
-    has_xdist = True
-except ImportError:
-    has_xdist = False
-
 
 def pytest_addoption(parser):
     group = parser.getgroup("sqlalchemy")
@@ -75,6 +69,9 @@ def pytest_addoption(parser):
 
 
 def pytest_configure(config):
+    if config.pluginmanager.hasplugin("xdist"):
+        config.pluginmanager.register(XDistHooks())
+
     if hasattr(config, "workerinput"):
         plugin_base.restore_important_follower_config(config.workerinput)
         plugin_base.configure_follower(config.workerinput["follower_ident"])
@@ -148,10 +145,8 @@ def pytest_collection_finish(session):
         collect_types.init_types_collection(filter_filename=_filter)
 
 
-if has_xdist:
-    import uuid
-
-    def pytest_configure_node(node):
+class XDistHooks:
+    def pytest_configure_node(self, node):
         from sqlalchemy.testing import provision
         from sqlalchemy.testing import asyncio
 
@@ -166,7 +161,7 @@ if has_xdist:
             provision.create_follower_db, node.workerinput["follower_ident"]
         )
 
-    def pytest_testnodedown(node, error):
+    def pytest_testnodedown(self, node, error):
         from sqlalchemy.testing import provision
         from sqlalchemy.testing import asyncio