_search_regex's "isatty" call fails with Py2exe's

_search_regex calls the sys.stderr.isatty() function for unix systems.

Py2exe uses a custom Stderr() stream which doesn't have an `isatty()`
function, leading to it's crash.

Fixes easily with checking that it's a unix system first.

youtube_dl/extractor/common.py

@@ -292,7 +292,7 @@ class InfoExtractor(object):
                 mobj = re.search(p, string, flags)
                 if mobj: break
 
-        if sys.stderr.isatty() and os.name != 'nt':
+        if os.name != 'nt' and sys.stderr.isatty():
             _name = u'\033[0;34m%s\033[0m' % name
         else:
             _name = name