[cwconfig] Trim down allowed exceptions in gettext language setting I can't see any valid reason to pass on ImportError and AttributeError. In particular, the latter shadowed a Python 3 error until 4f43e64603ef.

Release notes
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.. toctree::
    :maxdepth: 1

    3.23
    3.22
    3.21
    3.20
    3.19
    3.18
    3.17
    3.16
    3.15
    3.14