propagate translator function exceptions

The existing code tacitly uses the default translator
functions if a user-specified translator throws an
exception.  Propagate this exception instead so that
translator coders can know about them.
fix failing utf8 test

sp_usinas.shp seems to be latin-1, not utf8.  It contains the
sequence 0xc7,0xc8 which is not valid utf8.
sort default translations by key so tests pass reliably