Move all uses of `pool` inside `run_parallel()`.

This includes creating the pool, tearing it down under normal use, and
tearing it down in case of exception.

Doing this makes it harder to leak processes, as for instance was
happening in #410.

Fixes #410

1 files changed, 4 insertions, 2 deletions

diff --git a/tests/unit/test_checker_manager.py b/tests/unit/test_checker_manager.py
index 82fa3f8..e3d2379 100644
--- a/tests/unit/test_checker_manager.py
+++ b/tests/unit/test_checker_manager.py
@@ -22,17 +22,19 @@ def test_oserrors_cause_serial_fall_back():
     style_guide = style_guide_mock()
     with mock.patch('_multiprocessing.SemLock', side_effect=err):
         manager = checker.Manager(style_guide, [], [])
+        manager.run()
     assert manager.using_multiprocessing is False
 
 
 @mock.patch('flake8.utils.is_windows', return_value=False)
 def test_oserrors_are_reraised(is_windows):
-    """Verify that OSErrors will cause the Manager to fallback to serial."""
+    """Verify that unexpected OSErrors will cause the Manager to reraise."""
     err = OSError(errno.EAGAIN, 'Ominous message')
     style_guide = style_guide_mock()
     with mock.patch('_multiprocessing.SemLock', side_effect=err):
         with pytest.raises(OSError):
-            checker.Manager(style_guide, [], [])
+            manager = checker.Manager(style_guide, [], [])
+            manager.run()
 
 
 def test_multiprocessing_is_disabled():