This fail currently on travis and I can reproduce it locally. Here is a diff to get the test working:

(Kotti)j23d@twist:~/projects/Kotti$ git diff
diff --git a/kotti/tests/browser.txt b/kotti/tests/browser.txt
index 174b2a6..44837b3 100644
--- a/kotti/tests/browser.txt
+++ b/kotti/tests/browser.txt
@@ -761,9 +761,10 @@ set his own password:
   Your registration for Website des Kottbusser Tors
   >>> print email.body # doctest: +ELLIPSIS +NORMALIZE_WHITESPACE
   Hello, Bob Dabolina!
-  You have been invited to join Website des Kottbusser Tors.
-  Click here to set your password and log in:
-  http://localhost:6543/@@set-password?token=...
+  <BLANKLINE>
+  You are joining Website des Kottbusser Tors.
+  <BLANKLINE>
+  Click here to set your password and log in: http://localhost:6543/@@set-password?token=...
 
 We'll use that link to set our password:

Could you add this to your branch?