ImportError: cannot import name Namespace

I am trying to run the app.py from the examples folder inside a virtual environment with Python 2.7.

This is my output for running app.py:

$ python scripts/python/app.py
Traceback (most recent call last):
  File "scripts/python/app.py", line 4, in <module>
    from flask_socketio import SocketIO, emit, join_room, leave_room, \
  File "/home/username/.local/lib/python2.7/site-packages/flask_socketio/__init__.py", line 23, in <module>
    from .namespace import Namespace
  File "/home/username/.local/lib/python2.7/site-packages/flask_socketio/namespace.py", line 1, in <module>
    from socketio import Namespace as _Namespace
ImportError: cannot import name Namespace

I saw some comments suggesting a manual upgrade but that didn’t work for me:

pip install --upgrade flask-socketio                                                                                                                                                                       feature/pythonSocketServer [bac96ba] modified untracked
Requirement already up-to-date: flask-socketio in /home/username/.local/lib/python2.7/site-packages
Requirement already up-to-date: python-socketio>=1.6.1 in /home/username/.local/lib/python2.7/site-packages (from flask-socketio)
Requirement already up-to-date: Flask>=0.9 in /home/username/.local/lib/python2.7/site-packages (from flask-socketio)
Requirement already up-to-date: six>=1.9.0 in /usr/lib/python2.7/site-packages (from python-socketio>=1.6.1->flask-socketio)
Requirement already up-to-date: python-engineio>=1.2.1 in /home/username/.local/lib/python2.7/site-packages (from python-socketio>=1.6.1->flask-socketio)
Requirement already up-to-date: Jinja2>=2.4 in /usr/lib/python2.7/site-packages (from Flask>=0.9->flask-socketio)
Requirement already up-to-date: Werkzeug>=0.7 in /home/username/.local/lib/python2.7/site-packages (from Flask>=0.9->flask-socketio)
Requirement already up-to-date: click>=2.0 in /home/username/.local/lib/python2.7/site-packages (from Flask>=0.9->flask-socketio)
Requirement already up-to-date: itsdangerous>=0.21 in /home/username/.local/lib/python2.7/site-packages (from Flask>=0.9->flask-socketio)
Requirement already up-to-date: MarkupSafe>=0.23 in /usr/lib/python2.7/site-packages (from Jinja2>=2.4->Flask>=0.9->flask-socketio)

I have a setup.py file for my project which includes the following line:

install_requires=['pybluez', 'flask-socketio']

I also tried replacing my setup.py with the requirements.txt from here.