hook: do not redirect stdout/err/in to ui while running in-process hooks (BC)

It was introduced by a59058fd074a to address command-server issues. After
that, I've made a complete fix by 69f86b937035, so we don't need to replace
sys.stdio objects to protect the IPC channels.

This change means we no longer see data written to sys.stdout/err by an
in-process hook on command server. I think that's okay because the canonical
way is to use ui functions and in-process hooks should respect the Mercurial
API.

This will help Python 3 porting, where sys.stdout is TextIO but ui.fout is
BytesIO.

mercurial/hook.py

@@ -90,12 +90,6 def _pythonhook(ui, repo, name, hname, f
     starttime = time.time()
 
     try:
-        # redirect IO descriptors to the ui descriptors so hooks
-        # that write directly to these don't mess up the command
-        # protocol when running through the command server
-        old = sys.stdout, sys.stderr, sys.stdin
-        sys.stdout, sys.stderr, sys.stdin = ui.fout, ui.ferr, ui.fin
-
         r = obj(ui=ui, repo=repo, hooktype=name, **args)
     except Exception as exc:
         if isinstance(exc, error.Abort):
@@ -111,7 +105,6 def _pythonhook(ui, repo, name, hname, f
         ui.traceback()
         return True, True
     finally:
-        sys.stdout, sys.stderr, sys.stdin = old
         duration = time.time() - starttime
         ui.log('pythonhook', 'pythonhook-%s: %s finished in %0.2f seconds\n',
                name, funcname, duration)

tests/test-commandserver.t

@@ -236,8 +236,6 check that local configs for the cached
   ...                         'id'],
   ...                input=stringio('some input'))
   *** runcommand --config hooks.pre-identify=python:hook.hook id
-  hook talking
-  now try to read something: 'some input'
   eff892de26ec tip
 
   $ rm hook.py*