Thanks. I didn't know about the `pkg-config` thing. I just checked with pkg-config on macOS

`pkg-config --help` prints usage instructions to stdout

pkg-config followed by invalid options prints output to stderr, for example `pkg-config --asdf` prints `Unknown option --asdf` to stderr.

The PR I submitted does something similar, making both python and shell script versions of `python-config` to print out the usage instruction message to stdout when --help is provided and stderr when given invalid arguments.