Use contextlib for temporary py console overrides

Using context overrides means stdout/stderr overrides can't be left set by accident.

release/scripts/modules/console_python.py

@@ -136,18 +136,25 @@ def execute(context, is_interactive):
 
     console, stdout, stderr = get_console(hash(context.region))
 
-    # redirect output
-    sys.stdout = stdout
-    sys.stderr = stderr
-
-    # don't allow the stdin to be used, can lock blender.
-    stdin_backup = sys.stdin
-    sys.stdin = None
-
     if _BPY_MAIN_OWN:
         main_mod_back = sys.modules["__main__"]
         sys.modules["__main__"] = console._bpy_main_mod
 
+    # redirect output
+    from contextlib import (
+            redirect_stdout,
+            redirect_stderr,
+            )
+
+    # not included with Python
+    class redirect_stdin(redirect_stdout.__base__):
+        _stream = "stdin"
+
+    # don't allow the stdin to be used, can lock blender.
+    with redirect_stdout(stdout), \
+         redirect_stderr(stderr), \
+         redirect_stdin(None):
+
         # in case exception happens
         line = ""  # in case of encoding error
         is_multiline = False
@@ -174,8 +181,6 @@ def execute(context, is_interactive):
     output_err = stderr.read()
 
     # cleanup
-    sys.stdout = sys.__stdout__
-    sys.stderr = sys.__stderr__
     sys.last_traceback = None
 
     # So we can reuse, clear all data
@@ -213,9 +218,6 @@ def execute(context, is_interactive):
     if output_err:
         add_scrollback(output_err, 'ERROR')
 
-    # restore the stdin
-    sys.stdin = stdin_backup
-
     # execute any hooks
     for func, args in execute.hooks:
         func(*args)