swig python: [] throws exception

[markus2330]

[] throws an exception when a key does not exist:

    Traceback (most recent call last):
      File "example_kdb.py", line 10, in <module>
        key = ks["user/MyApp/mykey"]
      File "kdb.py", line 1172, in __getitem__
        raise KeyError(str(key))
    KeyError: 'user/MyApp/mykey'

When this is the intended behaviour, then the example should be changed to

    key = ks.lookup("user/MyApp/mykey")

Otherwise, [] should be changed.