This patch comes from upstream: http://bugs.python.org/issue26228

It has not yet been committed, but seems on track to be, and we need

it to fix a bug.

--- Python-2.7.13/Lib/pty.py.orig	2016-12-17 12:05:06.000000000 -0800

+++ Python-2.7.13/Lib/pty.py	2017-04-26 13:34:02.125867738 -0700

@@ -148,7 +148,7 @@

         if master_fd in rfds:

             data = master_read(master_fd)

             if not data:  # Reached EOF.

-                fds.remove(master_fd)

+                return

             else:

                 os.write(STDOUT_FILENO, data)

         if STDIN_FILENO in rfds:

@@ -164,7 +164,15 @@

         argv = (argv,)

     pid, master_fd = fork()

     if pid == CHILD:

-        os.execlp(argv[0], *argv)

+        try:

+            os.execlp(argv[0], *argv)

+        except:

+            # If we wanted to be really clever, we would use

+            # the same method as subprocess() to pass the error

+            # back to the parent.  For now just dump stack trace.

+            traceback.print_exc()

+        finally:

+            os._exit(1)

     try:

         mode = tty.tcgetattr(STDIN_FILENO)

         tty.setraw(STDIN_FILENO)

@@ -174,6 +182,10 @@

     try:

         _copy(master_fd, master_read, stdin_read)

     except (IOError, OSError):

+        # Some OSes never return an EOF on pty, just raise

+        # an error instead.

+        pass

+    finally:

         if restore:

             tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode)

--- Python-2.7.13/Lib/test/test_pty.py.orig	2016-12-17 12:05:06.000000000 +0000

+++ Python-2.7.13/Lib/test/test_pty.py	2017-04-26 13:39:11.397817862 +0000

@@ -270,7 +270,7 @@

         socketpair[1].close()

         os.close(write_to_stdin_fd)

-        # Expect two select calls, the last one will cause IndexError

+        # Expect two select calls, then a normal return on master EOF

         pty.select = self._mock_select

         self.select_rfds_lengths.append(2)

         self.select_rfds_results.append([mock_stdin_fd, masters[0]])

@@ -278,8 +278,7 @@

         # both encountered an EOF before the second select call.

         self.select_rfds_lengths.append(0)

-        with self.assertRaises(IndexError):

-            pty._copy(masters[0])

+        pty._copy(masters[0])

 def test_main(verbose=None):