support journalctl postfix log case

tests/test_email.py

@@ -91,7 +91,11 @@ def send_test_email():
     timeout = 120
     waited = 2
     out = ''
-    cmd = 'grep "%s" /var/log/mail.log' % email
+    if os.path.isfile('/var/log/mail.log'):
+        cmd = 'grep "%s" /var/log/mail.log' % email
+    else:
+        print('/var/log/mail.log not found, trying journalctl')
+        cmd = 'journalctl -u postfix | grep %s' % email
     while True:
         status, out = subprocess.getstatusoutput(cmd)
         if status == 0: