Fix faulthandler for Twisted Logger when used with "--capture=no"

The Twisted Logger will return an invalid file descriptor since it is
not backed by an FD. So, let's also forward this to the same code path
as with `pytest-xdist`.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/_pytest/faulthandler.py b/src/_pytest/faulthandler.py
index d0cc0430c..ff673b5b1 100644
--- a/src/_pytest/faulthandler.py
+++ b/src/_pytest/faulthandler.py
@@ -69,7 +69,12 @@ class FaultHandlerHooks:
     @staticmethod
     def _get_stderr_fileno():
         try:
-            return sys.stderr.fileno()
+            fileno = sys.stderr.fileno()
+            # The Twisted Logger will return an invalid file descriptor since it is not backed
+            # by an FD. So, let's also forward this to the same code path as with pytest-xdist.
+            if fileno == -1:
+                raise AttributeError()
+            return fileno
         except (AttributeError, io.UnsupportedOperation):
             # pytest-xdist monkeypatches sys.stderr with an object that is not an actual file.
             # https://docs.python.org/3/library/faulthandler.html#issue-with-file-descriptors