python 2.7 - Apache Airflow : airflow initdb results in "ImportError: No module named json"

Question

On Ubuntu 16.04 with Python 2.7 default version, I am trying to install Apache airflow but ran into several issues and currently I see on

apache initdb 
Traceback (most recent call last):
  File "/usr/local/bin/airflow", line 21, in <module>
    from airflow import configuration
  File "/usr/local/lib/python2.7/dist-packages/airflow/__init__.py", line 40, in <module>
    from flask_admin import BaseView
  File "/usr/local/lib/python2.7/dist-packages/flask_admin/__init__.py", line 6, in <module>
    from .base import expose, expose_plugview, Admin, BaseView, AdminIndexView  # noqa: F401
  File "/usr/local/lib/python2.7/dist-packages/flask_admin/base.py", line 6, in <module>
    from flask import Blueprint, current_app, render_template, abort, g, url_for
  File "/usr/local/lib/python2.7/dist-packages/flask/__init__.py", line 20, in <module>
    from .app import Flask
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 69, in <module>
    from .wrappers import Request
  File "/usr/local/lib/python2.7/dist-packages/flask/wrappers.py", line 14, in <module>
    from werkzeug.wrappers.json import JSONMixin as _JSONMixin
ImportError: No module named json

Tried these things till now:

$ sudo apt-get install build-essential autoconf libtool pkg-config python-opengl python-imaging python-pyrex python-pyside.qtopengl idle-python2.7 qt4-dev-tools qt4-designer libqtgui4 libqtcore4 libqt4-xml libqt4-test libqt4-script libqt4-network libqt4-dbus python-qt4 python-qt4-gl libgle3 python-dev

sudo pip install -U Werkzeug==0.14.1

sudo pip install -U Jinja2==2.10.1

Also tried

pip install jsonate

pip install json # (this did not work)

 python
Python 2.7.12 (default, Nov 12 2018, 14:36:49)
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import json
>>> exit()

Nothing worked so far.

Answer 1

Just upgrade flask. You can use this command:

sudo pip install --upgrade Flask