This is a forked version of flask from ~7 years ago. It has a (relatively) simple bug in it that is your job to now fix.
This requires Python 2.7.x (tested on Python 2.7.10 that comes preinstalled with OSX)
I'd recommend using a virtualenv:
virtualenv local
source ./local/bin/activate
Then install the dependencies:
pip install -e .
pip install jsonschema mock blinker pytest
Take a look at #1 and figure out how best to fix the bug.
Run tests with py.test tests/flask_tests.py