cv::format using locale decimal mark

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I'm using OpenCV 3.1 from C++ and I want to store my matrix in Python format:

errfile.open("errs.txt");
errfile << cv::format(errs, cv::Formatter::FMT_PYTHON) << std::endl;
errfile.close();

(errs is of type cv::Mat)

But the output is:

[[1271892,725376768, 65449,68687547074, 9149,382398115458, ... ]]

It seems like OpenCV is using my systems locale number format, using a comma as decimal separator. But Python expects a dot.

Although doing:

errfile << 6.66f << std::endl;

does print "6.66" not "6,66". Using errfile.embue to set the locale for the steam doesn't help either. I have to set the global locale:

std::setlocale(LC_NUMERIC, "en_US.UTF-8");

I don't think it makes sense to apply the locale here, since the format should be the python code format. Is this a bug I should report?

Additional Info: My system uses en_US locale for language, but German (de_AT) locale for numbers.