If this is not set it might default to calls to open() to use text mode
which is usually not wanted, and even wrong and leading to incorrect
results when loading binary .mpy files.
This also means that text files written and read will not have line-ending
translation from \n to \r\n and vice-versa anymore. This shouldn't be much
of a problem though since most tools dealing with text files adapt
automatically to any of the 2 formats.
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