Fix attrs redone (#3058)

* Catch deprecation warnings on import

* Fix deprecation warning from attrs

* Fix testcase

* Appease linters

* Fix test case

src/trio/_tests/test_trio.py

@@ -0,0 +1,8 @@
+def test_trio_import() -> None:
+    import sys
+
+    for module in list(sys.modules.keys()):
+        if module.startswith("trio"):
+            del sys.modules[module]
+
+    import trio  # noqa: F401

src/trio/_tests/tools/test_mypy_annotate.py

@@ -105,6 +105,8 @@ def test_endtoend(
     monkeypatch: pytest.MonkeyPatch,
     capsys: pytest.CaptureFixture[str],
 ) -> None:
+    import trio._tools.mypy_annotate as mypy_annotate
+
     inp_text = """\
 Mypy begun
 trio/core.py:15: error: Bad types here [misc]
@@ -116,7 +118,9 @@ def test_endtoend(
     with monkeypatch.context():
         monkeypatch.setattr(sys, "stdin", io.StringIO(inp_text))
 
-        main(["--dumpfile", str(result_file), "--platform", "SomePlatform"])
+        mypy_annotate.main(
+            ["--dumpfile", str(result_file), "--platform", "SomePlatform"]
+        )
 
     std = capsys.readouterr()
     assert std.err == ""

src/trio/_threads.py

@@ -139,7 +139,7 @@ def current_default_thread_limiter() -> CapacityLimiter:
 # system; see https://github.com/python-trio/trio/issues/182
 # But for now we just need an object to stand in for the thread, so we can
 # keep track of who's holding the CapacityLimiter's token.
-@attrs.frozen(eq=False, hash=False, slots=False)
+@attrs.frozen(eq=False, slots=False)
 class ThreadPlaceholder:
     name: str