Skip time-machine dep and spinner tests on PyPy

The time-machine package is deeply relying on CPython implementation
details and causes segfaults on PyPy.  Pull the dependency in only
on implementations other than PyPy, and skip collecting the spinner
tests on PyPy since they require it.

pyproject.toml

@@ -59,7 +59,7 @@ optional-dependencies.testing = [
   "pytest-mock>=3.10",
   "pytest-xdist>=3.1",
   "re-assert>=1.1",
-  "time-machine>=2.8.2",
+  "time-machine>=2.8.2; implementation_name != \"pypy\"",
 ]
 scripts.tox = "tox.run:run"
 dynamic = ["version"]

tests/conftest.py

@@ -39,6 +39,12 @@ def _fmt(msg: str) -> str:
     from typing_extensions import Protocol
 
 
+collect_ignore = []
+if sys.implementation.name == "pypy":
+    # time-machine causes segfaults on PyPy
+    collect_ignore.append("util/test_spinner.py")
+
+
 class ToxIniCreator(Protocol):
     def __call__(self, conf: str, override: Sequence[Override] | None = None) -> Config:  # noqa: U100
         ...