Fix for SF bug 601077 by Zack Weinberg.

The new execvpe code would sometimes do the wrong thing when a
non-executable file existed earlier in the path and an executable file
of the same name existed later in the path.  This patch restores the
proper behavior (which is to execute the second file).  When only a
non-executable file exists, the correct error is still reported.

Lib/os.py

@@ -309,7 +309,7 @@ def execvp(file, args):
     _execvpe(file, args)
 
 def execvpe(file, args, env):
-    """execv(file, args, env)
+    """execvpe(file, args, env)
 
     Execute the executable file (which is searched for along $PATH)
     with argument list args and environment env , replacing the
@@ -339,14 +339,21 @@ def _execvpe(file, args, env=None):
     else:
         envpath = defpath
     PATH = envpath.split(pathsep)
+    saved_exc = None
+    saved_tb = None
     for dir in PATH:
         fullname = path.join(dir, file)
         try:
             apply(func, (fullname,) + argrest)
-        except error, (errno, msg):
-            if errno != ENOENT and errno != ENOTDIR:
-                raise
-    raise error, (errno, msg)
+        except error, e:
+            tb = sys.exc_info()[2]
+            if (e.errno != ENOENT and e.errno != ENOTDIR
+                and saved_exc is None):
+                saved_exc = e
+                saved_tb = tb
+    if saved_exc:
+        raise error, saved_exc, saved_tb
+    raise error, e, tb
 
 # Change environ to automatically call putenv() if it exists
 try: