Fixed #30608 -- Fixed non-unicode EmailMessage crash when domain name for localhost is non-ASCII.

Assisted by felixxm.

django/core/mail/utils.py

@@ -4,6 +4,8 @@ Email message and email sending related helper functions.
 
 import socket
 
+from django.utils.encoding import punycode
+
 
 # Cache the hostname, but do it lazily: socket.getfqdn() can take a couple of
 # seconds, which slows down the restart of the server.
@@ -13,7 +15,7 @@ class CachedDnsName:
 
     def get_fqdn(self):
         if not hasattr(self, '_fqdn'):
-            self._fqdn = socket.getfqdn()
+            self._fqdn = punycode(socket.getfqdn())
         return self._fqdn