The PDFMiner project homepage states:
Written entirely in Python. (for version 2.4 or newer)
and further down:
Install Python 2.4 or newer. (Python 3 is not supported.)
so you'll have to install Python 2 to run this project.
Alternatively, you could try the Python 3 port, pdfminer3k
; it hasn't seen any updates in 20 months, while PDFMiner does have more recent releases, so your mileage may vary.