improve placeholder on login template

passbook/lib/utils/ui.py

@@ -0,0 +1,7 @@
+"""passbook UI utils"""
+
+def human_list(_list) -> str:
+    """Convert a list of items into 'a, b or c'"""
+    last_item = _list.pop()
+    result = ', '.join(_list)
+    return '%s or %s' % (result, last_item)