Thanks! I've pushed an updated to remove the affected line. Also, the version on the Python Package Index seems to be unaffected. This is mostly a development version, with tests run before being pushed over there, so if you want a more stable package, I recommend that (https://pypi.python.org/pypi/usgs-api). Still, I appreciate any time a bug is pointed out, so thank you!
Happy to help. I definitely want it to be usable. If you have contributions, feel free to submit. One thing I found out about after I built this was ulmo - quite a bit more robust and well documented. https://pypi.python.org/pypi/ulmo - I was searching beforehand and found nothing, but it looks great, though I have yet to use it.