code: final S3ObjectWrapper fetchInstructionFile(S3ObjectId s3ObjectId,
                                                 String instFileSuffix) {
          try {
              S3Object o = s3.getObject(
                  createInstructionGetRequest(s3ObjectId, instFileSuffix));
              return o == null ? null : new S3ObjectWrapper(o, s3ObjectId);
          } catch (AmazonServiceException e) {
              // If no instruction file is found, log a debug message, and return
              // null.
              if (log.isDebugEnabled()) {
                  log.debug("Unable to retrieve instruction file : "
                            + e.getMessage());
              }
              return null;
          }
      }
docs: Retrieves an instruction file from S3; or null if no instruction file is
  found.
  
  @param s3ObjectId
  the S3 object id (not the instruction file id)
  @param instFileSuffix
  suffix of the instruction file to be retrieved; or null to use
  the default suffix.
  @return an instruction file, or null if no instruction file is found.