Added better error handling in LogglySink

Updated the EmitBatchAsync method in LogglySink to handle potential exceptions and evaluate the LogResponse when calling the Log method of the LogglyClient.  It now writes to SelfLog when problems occur to enable easier debugging.

src/Serilog.Sinks.Loggly/Sinks/Loggly/LogglySink.cs

@@ -17,6 +17,7 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Loggly;
+using Serilog.Debugging;
 using Serilog.Events;
 using Serilog.Sinks.PeriodicBatching;
 
@@ -80,7 +81,24 @@ public LogglySink(IFormatProvider formatProvider, int batchSizeLimit, TimeSpan p
         /// not both.</remarks>
         protected override async Task EmitBatchAsync(IEnumerable<LogEvent> events)
         {
-            await _client.Log(events.Select(_converter.CreateLogglyEvent));
+            try
+            {
+                LogResponse response = await _client.Log(events.Select(_converter.CreateLogglyEvent)).ConfigureAwait(false);
+
+                switch (response.Code)
+                {
+                    case ResponseCode.Error:
+                        SelfLog.WriteLine("LogglySink received an Error response: {0}", response.Message);
+                        break;
+                    case ResponseCode.Unknown:
+                        SelfLog.WriteLine("LogglySink received an Unknown response: {0}", response.Message);
+                        break;
+                }
+            }
+            catch (Exception ex)
+            {
+                SelfLog.WriteLine("LogglySink encountered an exception: {0}", ex);
+            }
         }
 
     }