JSONDecodeError in apparently well formatted JSON

Hi, I'm getting the following `JSONDecodeError` but as far as I'm concerned this JSON is not ill formatted, therefore I shouldn't be getting the error I'm getting and shouldn't be connected with #246 or #248, am I missing something?

This is the error reported by `awslogs`:

```Version: 0.11.0
Python: 3.6.7 (default, Oct 22 2018, 11:32:17)
[GCC 8.2.0]
boto3 version: 1.7.47
Platform: Linux-4.15.0-52-generic-x86_64-with-Ubuntu-18.04-bionic
Config: {'aws_access_key_id': 'SENSITIVE', 'aws_secret_access_key': 'SENSITIVE', 'aws_session_token': 'SENSITIVE', 'aws_profile': 'SENSITIVE', 'aws_region': None, 'log_group_name': '/aws/elasticbeanstalk/predict-api-prod/var/log/eb-docker/containers/eb-current-app/stdouterr.log', 'log_stream_name': 'ALL', 'filter_pattern': None, 'watch': True, 'watch_interval': 1, 'output_group_enabled': True, 'output_stream_enabled': True, 'output_timestamp_enabled': False, 'output_ingestion_time_enabled': False, 'start': '5m', 'end': None, 'color': 'auto', 'query': 'EVENT', 'func': 'list_logs'}
Args: ['/home/user/.local/bin/awslogs', 'get', '/aws/elasticbeanstalk/myebs-env/var/log/eb-docker/containers/eb-current-app/stdouterr.log', 'ALL', '--watch', '--timestamps', '--query=EVENT']

Traceback (most recent call last):
File "/home/user/.local/lib/python3.6/site-packages/awslogs/bin.py", line 178, in main
getattr(logs, options.func)()
File "/home/user/.local/lib/python3.6/site-packages/awslogs/core.py", line 223, in list_logs
consumer()
File "/home/user/.local/lib/python3.6/site-packages/awslogs/core.py", line 206, in consumer
parsed = json.loads(event['message'])
File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
return _default_decoder.decode(s)
File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/usr/lib/python3.6/json/decoder.py", line 355, in raw_decode
obj, end = self.scan_once(s, idx)
json.decoder.JSONDecodeError: Expecting ',' delimiter: line 37 column 25 (char 1486)

```
The [`structlog`](http://www.structlog.org/en/stable/) log that reproduces this issue is:

```
{
"CALLER": "api.resources.post+880",
"EVENT": "Sending retrieved score to LP",
"HAPPENED_AT": "[+0000] 02/07/2019 09:56:16:059991",
"LEVEL": "INFO",
"application_scores": [
{
"applicationId": "1312558q184849",
"pred_app_score": 5.0
},
{
"applicationId": "1312558q184850",
"pred_app_score": 5.0
},
{
"applicationId": "1312558q184851",
"pred_app_score": 5.0
},
{
"applicationId": "1312558q184852",
"pred_app_score": 5.0
}
],
"bucket": 2.0,
"bucket_label": "HIGH",
"bucket_reason": "Based on prediction score.",
"candidate_id": 1312558,
"job_id": 44105,
"lp_url": "https://dtest.launchpadrecruitsapp.com/predict/scores/receive",
"model_id": 485,
"score": 5.0
```

Start at awslogs/core.py, where consumer() passes event['message'] to json.loads(), and compare that input with the supplied structlog payload and traceback. Reproduce the failure with the reported command and determine why this message reaches the parser; done means the cause and expected handling of this input are established.

Written by the indexing model from the issue text.