Our logging framework used to strnvisx(3) each and every line
iff it is written to a FILE. This is often unhelpful because
the line usually contains a number of elements that have already
been quoted and it makes the logs much more difficult to read in
this case. An example if krb5_unparse_name() which will already
quote most characters that one cares about.
We change the behaviour to simply drop unprintable characters
rather than encoding them. We thus rely on the rest of the
code to properly encode data elements written into the logs.
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