Werkzeug raises BrokenFilesystemWarning

Question

I get the following error when I send form data to my Flask app. It says it will use the UTF-8 encoding, but the locale is already UTF-8. What does this error mean?

/home/.virtualenvs/project/local/lib/python2.7/site-packages/werkzeug/filesystem.py:63:
BrokenFilesystemWarning: Detected a misconfigured UNIX filesystem:
Will use UTF-8 as filesystem encoding instead of 'ANSI_X3.4-1968'

$ locale
LANG=en_US.utf8
LANGUAGE=en_US.utf8
LC_CTYPE="en_US.utf8"
LC_NUMERIC="en_US.utf8"
LC_TIME="en_US.utf8"
LC_COLLATE="en_US.utf8"
LC_MONETARY="en_US.utf8"
LC_MESSAGES="en_US.utf8"
LC_PAPER="en_US.utf8"
LC_NAME="en_US.utf8"
LC_ADDRESS="en_US.utf8"
LC_TELEPHONE="en_US.utf8"
LC_MEASUREMENT="en_US.utf8"
LC_IDENTIFICATION="en_US.utf8"
LC_ALL=en_US.utf8

Answer 1

I saw this error too. After digging the code, I saw that this error is harmless and just a warning in /usr/local/lib/python2.7/dist-packages/werkzeug/filesystem.py:

        warnings.warn(
            'Detected a misconfigured UNIX filesystem: Will use UTF-8 as '
            'filesystem encoding instead of {0!r}'.format(rv),
            BrokenFilesystemWarning)

So, I would not worry about this warning.

Answer 2

This is not a critical error, just a warning that Werkzeug couldn't detect a good locale and so is using UTF-8 instead. This guess is probably correct.

See this Arch Linux wiki article for how to set up the locale correctly. It mentions that Python may see the ANSI_X3.4-1968 encoding even if the locale is properly configured, if you are running from certain environments such as Vim.

When executing :!python -c "import sys; print(sys.stdout.encoding)" in ViM, the output may be ANSI_X3.4-1968, even if the locale is set correctly everyhere. Set the PYTHONIOENCODING environment variable to utf-8 to remedy the situation.