procutil: split import and reassignment

Besides making the code clearer, it will reduce the diff in the next patch.

mercurial/utils/procutil.py

@@ -37,6 +37,11 b' from ..utils import resourceutil'
 
 osutil = policy.importmod('osutil')
 
+if pycompat.iswindows:
+    from .. import windows as platform
+else:
+    from .. import posix as platform
+
 
 def isatty(fp):
     try:
@@ -94,11 +99,8 b' if isatty(stdout):'
         stdout = os.fdopen(stdout.fileno(), 'wb', 1)
 
 if pycompat.iswindows:
-    from .. import windows as platform
+    stdout = platform.winstdout(stdout)
 
-    stdout = platform.winstdout(stdout)
-else:
-    from .. import posix as platform
 
 findexe = platform.findexe
 _gethgcmd = platform.gethgcmd