Replace simplejson exception
Replace simplejson exception

Currently, we raise the wrong error:
```
except json.JSONDecodeError:
    assert False, ...
AttributeError: 'module' object has no attribute 'JSONDecodeError'
```
This exception is from simplejson module. We use json

mnaboka/dcos,xinxian0458/dcos,BenWhitehead/dcos,dcos/dcos,mnaboka/dcos,mnaboka/dcos,jeid64/dcos,dcos/dcos,kensipe/dcos,darkonie/dcos,jeid64/dcos,xinxian0458/dcos,asridharan/dcos,branden/dcos,GoelDeepak/dcos,mesosphere-mergebot/dcos,vishnu2kmohan/dcos,dcos/dcos,dcos/dcos,darkonie/dcos,mnaboka/dcos,mellenburg/dcos,jeid64/dcos,vishnu2kmohan/dcos,amitaekbote/dcos,darkonie/dcos,mellenburg/dcos,kensipe/dcos,xinxian0458/dcos,lingmann/dcos,mesosphere-mergebot/mergebot-test-dcos,branden/dcos,mellenburg/dcos,darkonie/dcos,lingmann/dcos,branden/dcos,lingmann/dcos,asridharan/dcos,surdy/dcos,mesosphere-mergebot/dcos,BenWhitehead/dcos,vishnu2kmohan/dcos,GoelDeepak/dcos,mesosphere-mergebot/mergebot-test-dcos,vishnu2kmohan/dcos,amitaekbote/dcos,branden/dcos,amitaekbote/dcos,lingmann/dcos,surdy/dcos,xinxian0458/dcos,jeid64/dcos,dcos/dcos,amitaekbote/dcos,mnaboka/dcos,mesosphere-mergebot/dcos,kensipe/dcos,BenWhitehead/dcos,surdy/dcos,asridharan/dcos,GoelDeepak/dcos,darkonie/dcos,kensipe/dcos,mesosphere-mergebot/mergebot-test-dcos,surdy/dcos,mellenburg/dcos,asridharan/dcos,mesosphere-mergebot/dcos,mesosphere-mergebot/mergebot-test-dcos,BenWhitehead/dcos,GoelDeepak/dcos