fixed #11372 - potential `UnicodeDecodeError` with `subprocess.Popen()`

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Passing universal_newlines=True to subprocess.Popen() will implicitly perform decode(). But this might encounter errors which need to be ignored. Unfortunately the required options encoding and errors are not available until Python 3.6 so we still need to use decode() instead.

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Still a draft since I only have tested the daca client script so far.

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I have a different approach which tries to mitigate the errors instead of ignoring them. Needs some more testing though.