color: fix TypeError with auto mode on win32 when colors aren't available (issue2871)

This can happen when stdout isn't a terminal (e.g., it's being piped).

hgext/color.py

@@ -174,7 +174,8 def _modesetup(ui, opts):
             realmode = 'terminfo'
 
     if realmode == 'win32':
-        if not w32effects and mode == 'win32':
+        if not w32effects:
+            if mode == 'win32':
             # only warn if color.mode is explicitly set to win32
             ui.warn(_('warning: failed to set color mode to %s\n') % mode)
             return None