400 errors should show the actual error in the query

[rshivane]

Replication:
Fetch a missing metric using query API

Current behavior
The error raised does not indicate what is wrong with the query

Traceback (most recent call last):
  File "/home/ubuntu/Code/apptuit/tenants/bigbasket/es-glacier-snaphots/toktest.py", line 14, in <module>
    retry_count=3  # this will retry in case of 500 response or connection errors occur.
  File "/usr/local/lib/python2.7/dist-packages/apptuit/apptuit_client.py", line 362, in query
    "query service due to exception: %s" % str(http_error))
apptuit.apptuit_client.ApptuitException: Failed to get response from Apptuitquery service due to exception: 400 Client Error:  for url: https://api.apptuit.ai/api/query?start=1584607074&q=fetch%28%27missing_metric%27%29

Expectation
The API response has the error message that says the metric is missing. This message should be passed on to the API caller

{
   "status":"error",
   "message":"Query failed due to errors",
   "data":{
      "errors":[
         {
            "errorType":"ERROR_FETCHING_FROM_DATASOURCE",
            "queryLineNo":1,
            "queryColumnOffset":-1,
            "message":"Requested metrics(missing_metric) not found"
         }
      ]
   },
   "query_stats":{

   },
   "timing_diagnostics":[
   ],
   "query":{
      "querytext":"fetch('missing_metric')",
      "startTime":1584607112,
      "startTimeHumanReadableSYS":"March 19, 2020 8:38:32 AM UTC",
      "startTimeHumanReadableIST":"March 19, 2020 2:08:32 PM IST",
      "endTime":1584610762,
      "endTimeHumanReadableSYS":"March 19, 2020 9:39:22 AM UTC",
      "endTimeHumanReadableIST":"March 19, 2020 3:09:22 PM IST"
   }
}