Some messages written to stdout instead of stderr

[herring-swe]

autopep8 outputs some warnings and verbose messages to stdout instead of stderr.
This leads to problems when someone (such as vscode extension vscode-autopep8) wants to format not using --in-place flag since there's no distinction between output code and processing messages and thus writes the message into the new code..
See: microsoft/vscode-autopep8#201

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Command Line and Configuration

~/.config/pycodestyle

[pycodestyle]
max-complexity = 20

Command Line

$ python -m autopep8 -i file.py -vvv 2>/dev/null
read config path: /home/xyz/.config/pycodestyle
  unknown option 'max-complexity' ignored
$ python -m autopep8 -i file.py -vvv 1>/dev/null
[file:file.py]
--->  10 issue(s) to fix {'E221': {13, 14, 15, 16, 17, 18, 19}, 'E501': {72, 122, 100}}
--->  Not fixing E501 on line 72
--->  Not fixing E501 on line 100
--->  Not fixing E501 on line 122

Your Environment

• Python version: 2.0.4
• autopep8 version: 2.11.1

[hhatto]

This behaviour is part of what autopep8 does on the pycodestyle side when it runs pycodestyle.
It is difficult to fix on the autopep8 side.

https://github.com/PyCQA/pycodestyle/blob/710363bd2048d9c7fa3f24dcaf21e40ced7f74d5/pycodestyle.py#L2539

The first step in addressing this issue is to remove configuration options not supported by pycodestyle from the configuration file.