KeyError not caught

Question

I am a little confused by an error I have. I have some code that should retrieve a json file from a database and search it for a substring, representing a code. As I understand it, my query will have a corresponding code and then everything goes well, or my query will not have a corresponding code, and then my code will trigger a KeyError. I have written a try/except block catching this (expected) KeyError, but the error is not caught. What am I missing here?

Note: I just started dabbling with multiprocessing, is this related to that?

Here is the concerned code:

request_counter = 0
while request_counter < 3:
    try:
        if ' - reduced' in metabolite:
            metabolite = 'reduced ' + metabolite[:-10]
        cts_output = requests.get(
                        'http://cts.fiehnlab.ucdavis.edu/'
                        'service/convert/Chemical%20Name/'
                        'KEGG/' + metabolite)
        kegg_id = str(json.loads(cts_output.text)[0]['result'][0])
        metabolite_to_KEGG[bigg_id][kegg_id] = metabolite
        request_counter = 3
    except KeyError and IndexError:
        if request_counter == 2:
            metabolite_no_KEGG[bigg_id].append(metabolite)
        request_counter = request_counter + 1

This block is within a couple for loops.

Traceback:

Traceback (most recent call last): File "/Users/dcoukos/anaconda/lib/python3.6/multiprocessing/pool.py", line 119, in worker result = (True, func(*args, **kwds)) File "GetKeggs.py", line 131, in getBrendaKeggs kegg_id = str(json.loads(cts_output.text)[0]['result'][0]) KeyError: 'result' """

The above exception was the direct cause of the following exception:

Traceback (most recent call last): File "GetKeggs.py", line 223, in brenda_keggs.update(bk1.get()) File "/Users/dcoukos/anaconda/lib/python3.6/multiprocessing/pool.py", line 644, in get raise self._value KeyError: 'result'