Use assertRegex instead of assertIn to avoid non-determinism failures
    
    Depending on the system load, we might see messages containing "just
    now" or "seconds ago".  For example:
    
      "Merged just now..."
    
    vs.
    
      "Merged seconds ago..."
    
    If we only look for "just now", we are obviously going to fail when
    the system takes some time to process a request, and "seconds ago" is
    displayed.  This commit addresses this problem by using a regex when
    matching the text, and expecting both patterns.
    
    Fixes #4751
    
    Signed-off-by: Sergio Durigan Junior <sergiodj@sergiodj.net>