--- a/mercurial/mail.py	Tue May 04 13:28:42 2021 -0400
+++ b/mercurial/mail.py	Fri Apr 30 16:13:02 2021 -0700
@@ -269,7 +269,7 @@
 
 def codec2iana(cs):
     # type: (str) -> str
-    ''''''
+    ''' '''
     cs = email.charset.Charset(cs).input_charset.lower()
 
     # "latin1" normalizes to "iso8859-1", standard calls for "iso-8859-1"