Ack! I'll bet that's the problem. Our production Python (/opt/local/bin/python) was compiled without debug symbols. Desperate at one point to step through the interpreter's C code, I built my own, and installed it in my directory space. I forgot about that when packaging pylint. It was found before /opt/local/bin/python.
Let me see if fixing that solves the problem. My guess is that it will.