Should have been fixed in commit 85be1e5e7b when we updated the library, but was... missed.
travis caught it after the fact at least.
README
This example uses the USB port as a serial port and implements a loopback interface that immediately echos back whatever it receives. After flashing the evaluation board with the usbserial program and connecting it to a host computer with a USB cable, you can run the echo.py command as follows:
$ sudo ./echo.py hello world hello world $