Index: Doc/library/os.rst
===================================================================
--- Doc/library/os.rst	(révision 81227)
+++ Doc/library/os.rst	(copie de travail)
@@ -171,9 +171,11 @@
    Returns the list of directories that will be searched for a named
    executable, similar to a shell, when launching a process.
    *env*, when specified, should be an environment variable dictionary
-   to lookup the PATH in.
-   By default, when *env* is None, :data:`environ` is used.
+   to lookup the PATH in. Result type is str on Windows, bytes on Unix.
 
+   By default, when *env* is None, :data:`environ` is used on Windows or
+   :data:`environb` on Unix.
+
    .. versionadded:: 3.2
 
 
Index: Lib/os.py
===================================================================
--- Lib/os.py	(révision 81227)
+++ Lib/os.py	(copie de travail)
@@ -355,6 +355,8 @@
         return
     last_exc = saved_exc = None
     saved_tb = None
+    if not path.supports_unicode_filenames:
+        file = fsencode(file)
     for dir in get_exec_path(env):
         fullname = path.join(dir, file)
         try:
@@ -374,13 +376,36 @@
 def get_exec_path(env=None):
     """Returns the sequence of directories that will be searched for the
     named executable (similar to a shell) when launching a process.
+    Result type is str on Windows, bytes on Unix.
 
-    *env* must be an environment variable dict or None.  If *env* is None,
-    os.environ will be used.
+    env must be an environment variable dict or None. If env is None,
+    os.environ will be used on Windows or os.environb on Unix.
     """
     if env is None:
-        env = environ
-    return env.get('PATH', defpath).split(pathsep)
+        if supports_bytes_environ:
+            env = environb
+        else:
+            env = environ
+    try:
+        path_list = env.get('PATH')
+    except TypeError:
+        path_list = None
+    if supports_bytes_environ:
+        try:
+            path_listb = env[b'PATH']
+        except (KeyError, TypeError):
+            pass
+        else:
+            if path_list is not None:
+                raise ValueError(
+                    "env contains two PATH variables of different types")
+            path_list = path_listb
+    if path_list is None:
+        path_list = defpath
+    if path.supports_unicode_filenames:
+        return path_list.split(pathsep.encode('ascii'))
+    else:
+        return fsencode(path_list).split(pathsep.encode('ascii'))
 
 
 # Change environ to automatically call putenv(), unsetenv if they exist.
@@ -482,9 +507,11 @@
     The optional second argument can specify an alternate default.
     key, default and the result are str."""
     return environ.get(key, default)
-__all__.append("getenv")
 
-if name not in ('os2', 'nt'):
+supports_bytes_environ = name not in ('os2', 'nt')
+__all__.extend(("getenv", "supports_bytes_environ"))
+
+if supports_bytes_environ:
     def _check_bytes(value):
         if not isinstance(value, bytes):
             raise TypeError("bytes expected, not %s" % type(value).__name__)
@@ -504,7 +531,7 @@
         return environb.get(key, default)
     __all__.append("getenvb")
 
-if name != 'nt':
+if not path.supports_unicode_filenames:
     def fsencode(value):
         """Encode value for use in the file system, environment variables
         or the command line."""
Index: Lib/test/test_subprocess.py
===================================================================
--- Lib/test/test_subprocess.py	(révision 81227)
+++ Lib/test/test_subprocess.py	(copie de travail)
@@ -825,7 +825,23 @@
             stdout = stdout.rstrip(b'\n\r')
             self.assertEquals(stdout.decode('ascii'), repr(value))
 
+    def test_bytes_program(self):
+        path, program = os.path.split(sys.executable)
+        program = os.fsencode(program)
 
+        # bytes program, unicode PATH
+        env = os.environ.copy()
+        env["PATH"] = path
+        exitcode = subprocess.call([program, "-c", "pass"], env=env)
+        self.assertEquals(exitcode, 0)
+
+        # bytes program, bytes PATH
+        envb = os.environb.copy()
+        envb[b"PATH"] = os.fsencode(path)
+        exitcode = subprocess.call([program, "-c", "pass"], env=envb)
+        self.assertEquals(exitcode, 0)
+
+
 @unittest.skipUnless(mswindows, "Windows specific tests")
 class Win32ProcessTestCase(BaseTestCase):
 
Index: Lib/subprocess.py
===================================================================
--- Lib/subprocess.py	(révision 81227)
+++ Lib/subprocess.py	(copie de travail)
@@ -1096,15 +1096,14 @@
                                         for k, v in env.items()]
                         else:
                             env_list = None  # Use execv instead of execve.
+                        executable = os.fsencode(executable)
                         if os.path.dirname(executable):
-                            executable_list = (os.fsencode(executable),)
+                            executable_list = (executable,)
                         else:
                             # This matches the behavior of os._execvpe().
-                            path_list = os.get_exec_path(env)
-                            executable_list = (os.path.join(dir, executable)
-                                               for dir in path_list)
-                            executable_list = tuple(os.fsencode(exe)
-                                                    for exe in executable_list)
+                            executable_list = tuple(
+                                os.path.join(dir, executable)
+                                for dir in os.get_exec_path(env))
                         self.pid = _posixsubprocess.fork_exec(
                                 args, executable_list,
                                 close_fds, cwd, env_list,