Don't ignore JSON decoding errors

[jasonpaulos]

Summary

Currently if a JSON algod request cannot parse the response, it just returns None:

py-algorand-sdk/algosdk/v2client/algod.py

Lines 81 to 84 in 6b304e4

	try:
	return json.load(resp)
	except json.JSONDecodeError:
	return None

Scope

We should really return an error message in this case instead.

Urgency

It's important to display the proper error if decoding is unsuccessful.

[jkschin]

Hey @jasonpaulos, are you taking PRs for this? I've got two ideas:

1. Instead of returning None, we raise json.JSONDecodeError.
2. Inside error.py, create a class named AlgodJSONDecodeError and customize the messages.

Is there a place I should be writing a test for this as well? I can't find it. Happy to contribute a short PR and get familiar with Algorand.

[jasonpaulos]

@jkschin we would definitely appreciate a PR for this! Currently there is no easy way to automate a test for this (unless we can mock algod 🤔), so in this case I'd be inclined to accept a PR without a test.