Kill individual worker process after timeout in test_build_meta

According to the Python docs, shutting down the process pool does not
terminate the tasks that are already running, so it is necessary to
manually kill the individual processes in the pool.

Author: abravalheri

setuptools/tests/test_build_meta.py

@@ -2,6 +2,7 @@
 import shutil
 import tarfile
 import importlib
+import multiprocessing
 from concurrent import futures
 import re
 
@@ -39,6 +40,7 @@ def method(*args, **kw):
                 return task.result(TIMEOUT)
             except futures.TimeoutError:
                 self.pool.shutdown(wait=False)
+                caller.shutdown()  # pool.shutdown doesn't stop running processes
                 pytest.xfail(f"Backend did not respond before timeout ({TIMEOUT} s)")
 
         return method
@@ -47,12 +49,14 @@ def method(*args, **kw):
 class BuildBackendCaller(BuildBackendBase):
     def __init__(self, *args, **kwargs):
         super(BuildBackendCaller, self).__init__(*args, **kwargs)
+        self._process = None
 
         (self.backend_name, _,
          self.backend_obj) = self.backend_name.partition(':')
 
     def __call__(self, name, *args, **kw):
         """Handles aribrary function invocations on the build backend."""
+        self._process = multiprocessing.current_process()
         os.chdir(self.cwd)
         os.environ.update(self.env)
         mod = importlib.import_module(self.backend_name)
@@ -64,6 +68,10 @@ def __call__(self, name, *args, **kw):
 
         return getattr(backend, name)(*args, **kw)
 
+    def shutdown(self):
+        if self._process and self._process.is_alive():
+            self._process.kill()
+
 
 defns = [
     {