Remove redundant error log MISSING_SEGMENT_MSG

Refer to #316

Author: wangzlei

aws_xray_sdk/core/context.py

@@ -120,7 +120,6 @@ def handle_context_missing(self):
         Called whenever there is no trace entity to access or mutate.
         """
         if self.context_missing == 'RUNTIME_ERROR':
-            log.error(MISSING_SEGMENT_MSG)
             raise SegmentNotFoundException(MISSING_SEGMENT_MSG)
         else:
             log.error(MISSING_SEGMENT_MSG)