Fix issue with subprocess.Popen not producing any output

Src/StdLib/Lib/subprocess.py

@@ -1060,7 +1060,7 @@ def _get_handles(self, stdin, stdout, stderr):
                 errread, errwrite = _winapi.CreatePipe(None, 0)
                 errread, errwrite = Handle(errread), Handle(errwrite)
             elif stderr == STDOUT:
-                errwrite = c2pwrite
+                errwrite = int(c2pwrite) # ironpython: cast to int to prevent closing in _make_inheritable
             elif stderr == DEVNULL:
                 errwrite = msvcrt.get_osfhandle(self._get_devnull())
             elif isinstance(stderr, int):

Tests/test_regressions.py

@@ -1710,4 +1710,15 @@ def test_ipy3_gh1649(self):
     def test_map_type_int(self):
         self.assertEqual(list(map(type, [0])), [type(0)])
 
+    def test_ipy3_gh1135(self):
+        # https://github.com/IronLanguages/ironpython3/issues/1135
+        import sys
+        import subprocess
+        with subprocess.Popen([sys.executable, '-c', 'print("aaa", end="")'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT) as p:
+            out, err = p.communicate()
+
+        # ensure out is the expected value and not empty
+        self.assertEqual(out, b"aaa")
+
+
 run_test(__name__)