SysCaptureBinary: decode in writeorg

Fixes #6871.

Author: blueyed

changelog/6871.bugfix.rst

@@ -0,0 +1 @@
+Fix crash with captured output when using the :fixture:`capsysbinary fixture <capsysbinary>`.

src/_pytest/capture.py

@@ -681,7 +681,8 @@ def resume(self):
         setattr(sys, self.name, self.tmpfile)
         self._state = "resumed"
 
-    def writeorg(self, data):
+    def writeorg(self, data: str) -> None:
+        data = data.decode(self._old.encoding)
         self._old.write(data)
         self._old.flush()
 
@@ -695,6 +696,10 @@ def snap(self):
         self.tmpfile.truncate()
         return res
 
+    def writeorg(self, data: str) -> None:
+        self._old.write(data)
+        self._old.flush()
+
 
 class TeeSysCapture(SysCapture):
     def __init__(self, fd, tmpfile=None):

testing/test_capture.py

@@ -542,18 +542,31 @@ def test_hello(capfdbinary):
         reprec.assertoutcome(passed=1)
 
     def test_capsysbinary(self, testdir):
-        reprec = testdir.inline_runsource(
+        p1 = testdir.makepyfile(
             """\
             def test_hello(capsysbinary):
                 import sys
+
                 # some likely un-decodable bytes
                 sys.stdout.buffer.write(b'\\xfe\\x98\\x20')
+
                 out, err = capsysbinary.readouterr()
                 assert out == b'\\xfe\\x98\\x20'
                 assert err == b''
+
+                # handles writing strings
+                print("hello")
+                print("hello stderr", file=sys.stderr)
             """
         )
-        reprec.assertoutcome(passed=1)
+        result = testdir.runpytest(str(p1), "-rA")
+        result.stdout.fnmatch_lines([
+            "*- Captured stdout call -*",
+            "hello",
+            "*- Captured stderr call -*",
+            "hello stderr",
+            "*= 1 passed in *",
+        ])
 
     def test_partial_setup_failure(self, testdir):
         p = testdir.makepyfile(