Improve preferred encoding detection method

youtube-dl

@@ -33,15 +33,15 @@ def preferredencoding():
 	Returns the best encoding scheme for the system, based on
 	locale.getpreferredencoding() and some further tweaks.
 	"""
+	def yield_preferredencoding():
 		try:
 			pref = locale.getpreferredencoding()
-		# Mac OSX systems have this problem sometimes
-		if pref == '':
-			return 'UTF-8'
-		return pref
+			u'TEST'.encode(pref)
 		except:
-		sys.stderr.write('WARNING: problem obtaining preferred encoding. Falling back to UTF-8.\n')
-		return 'UTF-8'
+			pref = 'UTF-8'
+		while True:
+			yield pref
+	return yield_preferredencoding().next()
 
 class DownloadError(Exception):
 	"""Download Error exception.