title: U-SQL extraction failure for gz with custom JsonExtractor
body: <p>I am getting an exception during extraction whilst attempting to use the custom <code>JsonExtractor</code> from the <code>Microsoft.Analytics.Samples.Formats</code> library with a gzipped file.</p>
  
  <pre><code>Microsoft.Cosmos.ScopeStudio.BusinessObjects.Debugger.ScopeDebugExceptionwasunhandledMessage: Anunhandledexceptionoftype'Microsoft.Cosmos.ScopeStudio.BusinessObjects.Debugger.ScopeDebugException'occurredinMicrosoft.Cosmos.ScopeStudio.BusinessObjects.Debugger.dllAdditionalinformation: {
      "diagnosticCode": 195887142,
      "severity": "Error",
      "component": "RUNTIME",
      "source": "User",
      "errorId": "E_RUNTIME_USER_UNHANDLED_EXCEPTION_FROM_USER_CODE",
      "message": "An unhandled exception from user code has been reported when invoking the method 'Extract' on the user type 'Microsoft.Analytics.Samples.Formats.Json.JsonExtractor'",
      "description": "Unhandled exception from user code: \"Unexpected character encountered while parsing number: j. Path '', line 1, position 33.\"\nThe details includes more information including any inner exceptions and the stack trace where the exception was raised.",
      "resolution": "Make sure the bug in the user code is fixed.",
      "helpLink": "",
      "details": "==== Caught exception Newtonsoft.Json.JsonReaderException
         at Newtonsoft.Json.JsonTextReader.ReadNumberIntoBuffer()
         at Newtonsoft.Json.JsonTextReader.ParseNumber(ReadType readType)
         at Newtonsoft.Json.JsonTextReader.ParseValue()
         at Microsoft.Analytics.Samples.Formats.Json.JsonExtractor.&lt;Extract&gt;d__2.MoveNext()
         at ScopeEngine.SqlIpExtractor&lt;ScopeEngine::GZipInput,Extract_0_Data0&gt;.GetNextRow(SqlIpExtractor&lt;ScopeEngine::GZipInput23644,Extract_0_Data0&gt;* , Extract_0_Data0* output) in c:23644projects23644data-insights23644data_insights_ingestion_service23644datainsights.internalbi.scripts23644bin23644debug23644746497ac301de51323644n-populateaccountcurrencycodes.usql.debug_6b364b066929ac9723644sqlmanaged.h:line 1873",
      "internalDiagnostics": ""
  }
  </code></pre>
  
  <p>The extraction is successful if the JSON files are passed without gzipping them.</p>
  
  <p>I have also tested gzipped csv files, they seem to work just fine.
  This is encountered during a LocalRun. I haven't submitted this particular script to the cloud yet.</p>