[issue46186] replace `io.IncrementalNewlineDecoder` with non incremental newline decoders

[Guo Ci Teo]

New submission from Guo Ci Teo <zguoci at gmail.com>:

replace unnecessary use of `io.IncrementalNewlineDecoder` in code.
Some uses of the `decode` method were also incorrect without the `final=True` argument.

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messages: 409235
nosy: guoci
priority: normal
severity: normal
status: open
title: replace `io.IncrementalNewlineDecoder` with non incremental newline decoders

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue46186>
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