C++ library uses stout for error instead of stderr

[KevinCCucumber]

When testing the outputs, I experienced a bug where an error would be printed into the std output instead of the error output.
I found it by chance in the latest diff:

pyA2L/pya2l/extensions/a2lparser.hpp

Line 259 in 62fd04d

std::cout << "[ERROR (pya2l.A2LParser)] " << "Invalid param: " << parameter.get_name() << " -- " << token->toString() << std::endl;

Additionally, I have the error "enumeration 'Type' must be one of......." printed in the stdout:

I don't know where this gets imported or what other error cases are related here.