Fix #76735: Incorrect message in fopen on invalid mode

We have to log errors in `stream_opener` callbacks to the wrapper's
error log, because otherwise we may pick up an unrelated `errno

Fix #76735: Incorrect message in fopen on invalid mode

We have to log errors in `stream_opener` callbacks to the wrapper's
error log, because otherwise we may pick up an unrelated `errno` or a
most generic message.

Closes GH-6187.

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