Feedback welcome, particularly with regard to I/O in the harness.
I performed local functional testing of the harness by copying some request strings from picohttpparser's test.c into Python bytestrings, writing them out to 1 file per request, and running the uninstrumented and instrumented binaries in the Docker container with those files as arguments.
test.cinto Python bytestrings, writing them out to 1 file per request, and running the uninstrumented and instrumented binaries in the Docker container with those files as arguments.