fix(capture): swev-id: pytest-dev__pytest-5262 normalize EncodedFile mode

src/_pytest/capture.py

@@ -447,6 +447,20 @@ def name(self):
         """Ensure that file.name is a string."""
         return repr(self.buffer)
 
+    @property
+    def mode(self):
+        """
+        Present a text-like mode to callers.
+
+        The underlying buffer is opened in binary mode (e.g., 'rb+', 'wb+')
+        during fd-level capturing. Some libraries (e.g., youtube-dl) inspect
+        file.mode to decide whether to write bytes or text. Since EncodedFile
+        expects text on Python 3, report a mode without the binary flag.
+        """
+        m = getattr(self.buffer, "mode", "")
+        return m.replace("b", "")
+
+
     def __getattr__(self, name):
         return getattr(object.__getattribute__(self, "buffer"), name)
 

testing/test_capture.py

@@ -1194,6 +1194,14 @@ class TestStdCaptureFD(TestStdCapture):
     pytestmark = needsosdup
     captureclass = staticmethod(StdCaptureFD)
 
+    def test_stdout_mode(self):
+        with self.getcapture():
+            assert hasattr(sys.stdout, "buffer")
+            # underlying buffer is binary
+            assert "b" in sys.stdout.buffer.mode
+            # EncodedFile.mode should not include "b"
+            assert "b" not in sys.stdout.mode
+
     def test_simple_only_fd(self, testdir):
         testdir.makepyfile(
             """