Fixed UP031 (printf-string-formatting): Use format specifiers instead of percent format

tests/test_smtp_server.py

@@ -6,11 +6,11 @@ if len(sys.argv) < 3:
         sys.exit(1)
 
 host, toaddr, fromaddr = sys.argv[1:4]
-msg = """From: %s
-To: %s
+msg = """From: {}
+To: {}
 Subject: SMTP server test
 
-This is a test message.""" % (fromaddr, toaddr)
+This is a test message.""".format(fromaddr, toaddr)
 
 server = smtplib.SMTP(host, 25)
 server.set_debuglevel(1)