mod_http_oauth2: Gracefully handle cache write failure Would previously have thrown an error and probably returned a traceback. This would only happen if a *lot* of authorization codes were requested in a short interval.

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summary: Log a message once per minute
...

This module sends `-- MARK --` to the log once per minute. This may be
useful to give a sense of how busy the server is or see that logging and
timers are still working.