Using the following code I was able to open your JSON and print it. Save your JSON to temp.json and try this:

import json

with open("temp.json", "r") as infile:
    data = json.loads(infile.read())

print(data)

There is a rule in Python programming called "it is Easier to Ask for Forgiveness than for Permission" (in short: EAFP). It means that you should catch exceptions instead of checking values for validity.

Thus, try the following:

try:
    qByUser = byUsrUrlObj.read()
    qUserData = json.loads(qByUser).decode('utf-8')
    questionSubjs = qUserData["all"]["questions"]
except ValueError:  # includes simplejson.decoder.JSONDecodeError
    print('Decoding JSON has failed')

EDIT: Since simplejson.decoder.JSONDecodeError actually inherits from ValueError (proof here), I simplified the catch statement by just using ValueError.

There is likely a UTF-8 BOM encoded at the beginning of the file since it is complaining about the first byte. Open with encoding='utf-8-sig' and it will be removed if present:

Copy>>> import json
>>> data = {}
>>> with open('test.json','w',encoding='utf-8-sig') as f:  # write data with BOM
...   json.dump(data,f)
...
>>> with open('test.json') as f:  # read it back
...  data2 = json.load(f)
...
Traceback (most recent call last):
  <traceback removed>
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)  # same error
>>> with open('test.json',encoding='utf-8-sig') as f:
...  data2 = json.load(f)
...
>>> # worked

Your code produced an empty response body; you'd want to check for that or catch the exception raised. It is possible the server responded with a 204 No Content response, or a non-200-range status code was returned (404 Not Found, etc.). Check for this.

Note:

• There is no need to decode a response from UTF8 to Unicode, the json.loads() method can handle UTF8-encoded data natively.

• pycurl has a very archaic API. Unless you have a specific requirement for using it, there are better choices.

Either requests or httpx offer much friendlier APIs, including JSON support.

If you can, replace your call with the following httpx code:

import httpx

response = httpx.get(url)
response.raise_for_status()  # raises exception when not a 2xx response
if response.status_code != 204:
    return response.json()

Of course, this won't protect you from a URL that doesn't comply with HTTP standards; when using arbitrary URLs where this is a possibility, check if the server intended to give you JSON by checking the Content-Type header, and for good measure catch the exception:

if (
    response.status_code != 204 and
    response.headers["content-type"].strip().startswith("application/json")
):
    try:
        return response.json()
    except ValueError:
        # decide how to handle a server that's misbehaving to this extent

Iterate over the file, loading each line as JSON in the loop:

tweets = []
with open('tweets.json', 'r') as file:
    for line in file:
        tweets.append(json.loads(line))

This avoids storing intermediate python objects. As long as you write one full tweet per append() call, this should work.