feat(candle): better cuda error (huggingface#300)

Author: OlivierDehaene

backends/candle/src/lib.rs

@@ -18,6 +18,7 @@ use crate::models::{
 use crate::models::{
     FlashBertModel, FlashDistilBertModel, FlashJinaBertModel, FlashNomicBertModel,
 };
+use anyhow::Context;
 use candle::{DType, Device};
 use candle_nn::VarBuilder;
 use models::BertConfig;
@@ -55,9 +56,11 @@ impl CandleBackend {
     ) -> Result<Self, BackendError> {
         // Load config
         let config: String = std::fs::read_to_string(model_path.join("config.json"))
-            .map_err(|err| BackendError::Start(err.to_string()))?;
+            .context("Unable to read config file")
+            .map_err(|err| BackendError::Start(format!("{err:?}")))?;
         let config: Config = serde_json::from_str(&config)
-            .map_err(|err| BackendError::Start(format!("Model is not supported: {}", err)))?;
+            .context("Model is not supported")
+            .map_err(|err| BackendError::Start(format!("{err:?}")))?;
 
         // Get candle device
         let device = if candle::utils::cuda_is_available() {
@@ -72,7 +75,7 @@ impl CandleBackend {
                     )))
                 }
                 Err(err) => {
-                    tracing::warn!("Could not find a compatible CUDA device on host: {err}");
+                    tracing::warn!("Could not find a compatible CUDA device on host: {err:?}");
                     tracing::warn!("Using CPU instead");
                     Ok(Device::Cpu)
                 }