when error msg formatting fails, return error->DebugString

[liufengwei0103]

when error formatting fails, return error->DebugString

error_msg format 失败后（图片来自error format相关函数抛异常后）：

error_msg format 成功：

[lixinqi]

这个处理虽然看着拧巴，但其实很细腻。

[lixinqi]

以后的代码质量应该向这里看齐。

[github-actions]

Speed stats:

GPU Name: GeForce GTX 1080 

PyTorch resnet50 time: 141.9ms (= 7094.7ms / 50, input_shape=[16, 3, 224, 224], backward is enabled)
OneFlow resnet50 time: 128.3ms (= 6414.1ms / 50, input_shape=[16, 3, 224, 224], backward is enabled)
Relative speed: 1.11 (= 141.9ms / 128.3ms)

PyTorch resnet50 time: 85.7ms (= 4287.5ms / 50, input_shape=[8, 3, 224, 224], backward is enabled)
OneFlow resnet50 time: 74.6ms (= 3728.9ms / 50, input_shape=[8, 3, 224, 224], backward is enabled)
Relative speed: 1.15 (= 85.7ms / 74.6ms)

PyTorch resnet50 time: 59.6ms (= 2980.8ms / 50, input_shape=[4, 3, 224, 224], backward is enabled)
OneFlow resnet50 time: 48.5ms (= 2422.5ms / 50, input_shape=[4, 3, 224, 224], backward is enabled)
Relative speed: 1.23 (= 59.6ms / 48.5ms)

PyTorch resnet50 time: 49.8ms (= 2487.6ms / 50, input_shape=[2, 3, 224, 224], backward is enabled)
OneFlow resnet50 time: 38.7ms (= 1935.6ms / 50, input_shape=[2, 3, 224, 224], backward is enabled)
Relative speed: 1.29 (= 49.8ms / 38.7ms)

PyTorch resnet50 time: 41.6ms (= 2079.1ms / 50, input_shape=[1, 3, 224, 224], backward is enabled)
OneFlow resnet50 time: 37.3ms (= 1864.9ms / 50, input_shape=[1, 3, 224, 224], backward is enabled)
Relative speed: 1.11 (= 41.6ms / 37.3ms)