json parse error when the server returns non-json content

[mustafaatikshpfy]

Issue summary

I encountered a case where the server returned with HTTP 504 Timeout error
and the shopify_api gem tried to parse the response body as json, failed and
raised JSON::ParserError

As far as I understand, we expect the API to return always json response body
but there can be cases like accessing the API via a reverse proxy which can
respond with non-json body. In such cases, can't we still return a specific error
rather than JsonParse?

• shopify_api version: 10.x (although this should happen in the latest, 12.x version)
• Ruby version:
• Operating system:

Expected behavior

Actual behavior

Steps to reproduce the problem

1. stub the request in a test returning 504 with a non-json response body.
2. confirm you get a jsonparse error

[kaarelss]

This PR should fix it. Related to #1107 & #1091

[nelsonwittwer]

Closing as #1113 should have fixed this issue. Please re-open if the latest version doesn't solve this issue! thanks!