json.load causing IndexError: list index out of range

[WallyZ]

I'm trying to debug the ubuntu-mate-welcome python script which is refusing to load a valid json file.

I have validated the json file with jsonlint. However my experience with python is limited.

My environment is Ubuntu 18.04 aarch64 (arm64).

I have isolated the problem code in an example included here:

#! /usr/bin/python3
import sys
import json

print(sys.path)

json_path = ''

try:
    print('Reading index...')
    json_path = '/usr/share/ubuntu-mate-welcome/js/applications.json'
    with open(json_path) as data_file:
        print('Loading JSON.')
        index = json.load(data_file)
        print('LOADED JSON!!!!')
except Exception as e:
    index = None
    print('Software Index JSON is invalid or missing!')
    print(json_path)

The output is as follows:

Output:
['/home/odroid/Scripts', '/usr/lib/python36.zip', '/usr/lib/python3.6', '/usr/lib/python3.6/lib-dynload', '/usr/local/lib/python3.6/dist-packages', '/usr/lib/python3/dist-packages']
Reading index...
Loading JSON.
Software Index JSON is invalid or missing!
/usr/share/ubuntu-mate-welcome/js/applications.json

However my example does not display the :

Error:
IndexError: list index out of range

So I am not certain I have faithfully reproduced the problem!

Output from jsonlint-php:

Output:
jsonlint-php /usr/share/ubuntu-mate-welcome/js/applications.json
Valid JSON (/usr/share/ubuntu-mate-welcome/js/applications.json)

I have looked in the python path but cannot identify the json module referred to in the import statement.

How can I be certain I have the json module installed?