feat: add explicit BSP export error (#871)

Author: robertlaurin

sdk/lib/opentelemetry/sdk/trace/export.rb

@@ -10,6 +10,8 @@ module Trace
       # The Export module contains the built-in exporters and span processors for the OpenTelemetry
       # reference implementation.
       module Export
+        ExportError = Class.new(OpenTelemetry::Error)
+
         # Result codes for the SpanExporter#export method and the SpanProcessor#force_flush and SpanProcessor#shutdown methods.
 
         # The operation finished successfully.

sdk/lib/opentelemetry/sdk/trace/export/batch_span_processor.rb

@@ -194,7 +194,7 @@ def report_result(result_code, batch)
               @metrics_reporter.add_to_counter('otel.bsp.export.success')
               @metrics_reporter.add_to_counter('otel.bsp.exported_spans', increment: batch.size)
             else
-              OpenTelemetry.handle_error(message: "Unable to export #{batch.size} spans")
+              OpenTelemetry.handle_error(exception: ExportError.new("Unable to export #{batch.size} spans"))
               @metrics_reporter.add_to_counter('otel.bsp.export.failure')
               report_dropped_spans(batch.size, reason: 'export-failure')
             end