FYI: this is NOT a duplicate!
Before running my python code I installed biopython in the cmd prompt:
pip install biopython
I then
I just hit this issue with the problem being lower-case bio vs upper-case Bio. Turns out the problem was that it installs differently on python 2 and 3. In Python 2 you do import Bio, but in python 3 import bio. If you're hitting this issue it might be for the same reason, and the solution is probably to make sure you use the right name for the Python version you're on.