[BUG]训练自定义数据集时在数据增强部分挂掉，显示Error: Blocking queue is killed because the data reader raises an exception

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Checklist:

查找历史相关issue寻求解答/I have searched related issues but cannot get the expected help.
翻阅FAQ /I have read the FAQ documentation but cannot get the expected help.
确认bug是否在新版本里还未修复/The bug has not been fixed in the latest version.

描述问题/Describe the bug

A clear and concise description of what the bug is. 在训练自定义数据集时出现Error: Blocking queue is killed because the data reader raises an exception，此外还有、

复现/Reproduction

您使用的命令是？/What command or script did you run? python PaddleDetection-release-0.5/tools/train.py -c PaddleDetection-release-0.5/configs/ssd/ssd_mobilenet_v1_voc.yml
```
请填写命令/A placeholder for the command.
```
您是否更改过代码或配置文件？您是否理解您所更改的内容？还请您提供所更改的部分代码。/Did you make any modifications on the code or config? Did you understand what you have modified? Please provide the codes that you modified. 更改的代码有配置文件ssd——mobilnet——voc。yxml architecture: SSD pretrain_weights: https://paddlemodels.bj.bcebos.com/object_detection/ssd_mobilenet_v1_coco_pretrained.tar use_gpu: true max_iters: 20000 snapshot_iter: 180 log_iter: 30 metric: VOC map_type: 11point save_dir: output weights: output/ssd_mobilenet_v1_voc/model_final
20(label_class) + 1(background)

num_classes: 10

SSD: backbone: MobileNet multi_box_head: MultiBoxHead output_decoder: background_label: 0 keep_top_k: 200 nms_eta: 1.0 nms_threshold: 0.45 nms_top_k: 400 score_threshold: 0.01

MobileNet: norm_decay: 0. conv_group_scale: 1 conv_learning_rate: 0.1 extra_block_filters: [[256, 512], [128, 256], [128, 256], [64, 128]] with_extra_blocks: true

MultiBoxHead: aspect_ratios: [[2.], [2., 3.], [2., 3.], [2., 3.], [2., 3.], [2., 3.]] base_size: 300 flip: true max_ratio: 90 max_sizes: [[], 150.0, 195.0, 240.0, 285.0, 300.0] min_ratio: 20 min_sizes: [60.0, 105.0, 150.0, 195.0, 240.0, 285.0] offset: 0.5

LearningRate: schedulers:

!PiecewiseDecay milestones: [10000, 15000, 20000, 25000] values: [0.001, 0.0005, 0.00025, 0.0001, 0.00001]

OptimizerBuilder: optimizer: momentum: 0.0 type: RMSPropOptimizer regularizer: factor: 0.00005 type: L2

TrainReader: inputs_def: image_shape: [3, 320, 240] fields: ['image', 'gt_bbox', 'gt_class'] dataset: !VOCDataSet anno_path: train.txt dataset_dir: /home/aistudio/work/src/ImageSet use_default_label: false sample_transforms:

!DecodeImage to_rgb: true
!RandomDistort brightness_lower: 0.875 brightness_upper: 1.125 is_order: true
!RandomExpand fill_value: [127.5, 127.5, 127.5]
!RandomCrop allow_no_crop: false
!NormalizeBox {}
!ResizeImage interp: 1 target_size: 300 use_cv2: false
!RandomFlipImage is_normalized: true
!Permute {}
!NormalizeImage is_scale: false mean: [127.5, 127.5, 127.5] std: [127.502231, 127.502231, 127.502231] batch_size: 64 shuffle: true drop_last: true worker_num: 8 bufsize: 16 use_process: true

EvalReader: inputs_def: image_shape: [3, 320, 240] fields: ['image', 'gt_bbox', 'gt_class', 'im_shape', 'im_id', 'is_difficult'] dataset: !VOCDataSet anno_path: val.txt dataset_dir: /home/aistudio/work/src/ImageSet use_default_label: false sample_transforms:

!DecodeImage to_rgb: true
!NormalizeBox {}
!ResizeImage interp: 1 target_size: 300 use_cv2: false
!Permute {}
!NormalizeImage is_scale: false mean: [127.5, 127.5, 127.5] std: [127.502231, 127.502231, 127.502231] batch_size: 32 worker_num: 8 bufsize: 16 use_process: false

TestReader: inputs_def: image_shape: [3,320,240] fields: ['image', 'im_id', 'im_shape'] dataset: !ImageFolder anno_path: /home/aistudio/work/src/ImageSet/label_list.txt use_default_label: false sample_transforms:

!DecodeImage to_rgb: true
!ResizeImage interp: 1 max_size: 0 target_size: 300 use_cv2: true
!Permute {}
!NormalizeImage is_scale: false mean: [127.5, 127.5, 127.5] std: [127.502231, 127.502231, 127.502231] batch_size: 1

您使用的数据集是？/What dataset did you use? 自定义数据集，voc格式
请提供您出现的报错信息及相关log。/Please provide the error messages or relevant log information.

环境/Environment

请提供您使用的Paddle和PaddleDetection的版本号/Please provide the version of Paddle and PaddleDetection you use： Paddle1.8.4 Paddledetection0.5 python3.7 需要部署到edgeboardz3上
如您在使用PaddleDetection的同时还在使用其他产品，如PaddleServing、PaddleInference等，请您提供其版本号/ Please provide the version of any other related tools/products used, such as the version of PaddleServing and etc：
请提供您使用的操作系统信息，如Linux/Windows/MacOS /Please provide the OS information, e.g., Linux： win10
请问您使用的Python版本是？/ Please provide the version of Python you used.
请问您使用的CUDA/cuDNN的版本号是？/ Please provide the version of CUDA/cuDNN you used.

如果您的issue是关于安装或环境，您可以先查询安装文档尝试解决~

If your issue looks like an installation issue / environment issue, please first try to solve it yourself with the instructions in https://github.com/PaddlePaddle/PaddleDetection/blob/release/2.1/docs/tutorials/INSTALL.md

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