handle case msg is string in replace() (#1271)

should fix https://sentry.io/organizations/simplelogin/issues/3563106404/?alert_rule_id=2478639&alert_timestamp=1662404226476&alert_type=email&environment=production&project=1868546&referrer=alert_email

app/email_utils.py

@@ -994,7 +994,11 @@ def add_header(msg: Message, text_header, html_header=None) -> Message:
     return msg
 
 
-def replace(msg: Message, old, new) -> Message:
+def replace(msg: Union[Message, str], old, new) -> Union[Message, str]:
+    if type(msg) is str:
+        msg = msg.replace(old, new)
+        return msg
+
     content_type = msg.get_content_type()
 
     if (

tests/test_email_utils.py

@@ -460,6 +460,12 @@ Content-Type: text/html;	charset=us-ascii
     assert "old" not in new_msg.as_string()
 
 
+def test_replace_str():
+    msg = "a string"
+    new_msg = replace(msg, "a", "still a")
+    assert new_msg == "still a string"
+
+
 def test_generate_reply_email(flask_client):
     user = create_new_user()
     reply_email = generate_reply_email("test@example.org", user)