Add name of key to key upload errors

> example | Key upload failed: Error processing key "meow": I/O Error: No such file or directory (os error 2)

Fixes #101.

src/error.rs

@@ -34,8 +34,8 @@ pub enum ColmenaError {
     #[snafu(display("Validation error"))]
     ValidationError { errors: ValidationErrors },
 
-    #[snafu(display("Failed to upload keys: {}", error))]
-    KeyError { error: key::KeyError },
+    #[snafu(display("Error processing key \"{}\": {}", name, error))]
+    KeyError { name: String, error: key::KeyError },
 
     #[snafu(display("Store path {:?} is not a derivation", store_path))]
     NotADerivation { store_path: StorePath },
@@ -77,12 +77,6 @@ impl From<std::io::Error> for ColmenaError {
     }
 }
 
-impl From<key::KeyError> for ColmenaError {
-    fn from(error: key::KeyError) -> Self {
-        Self::KeyError { error }
-    }
-}
-
 impl From<ValidationErrors> for ColmenaError {
     fn from(errors: ValidationErrors) -> Self {
         Self::ValidationError { errors }

src/nix/host/key_uploader.rs

@@ -12,7 +12,7 @@ use shell_escape::unix::escape;
 use tokio::io::{AsyncWriteExt, BufReader};
 use tokio::process::Child;
 
-use crate::error::ColmenaResult;
+use crate::error::{ColmenaError, ColmenaResult};
 use crate::job::JobHandle;
 use crate::nix::Key;
 use crate::util::capture_stream;
@@ -32,7 +32,11 @@ pub fn generate_script<'a>(key: &'a Key, destination: &'a Path, require_ownershi
 }
 
 pub async fn feed_uploader(mut uploader: Child, key: &Key, job: Option<JobHandle>) -> ColmenaResult<()> {
-    let mut reader = key.reader().await?;
+    let mut reader = key.reader().await
+        .map_err(|error| ColmenaError::KeyError {
+            name: key.name().to_owned(),
+            error,
+        })?;
     let mut stdin = uploader.stdin.take().unwrap();
 
     tokio::io::copy(reader.as_mut(), &mut stdin).await?;

src/nix/key.rs

@@ -148,6 +148,7 @@ impl Key {
         }
     }
 
+    pub fn name(&self) -> &str { &self.name }
     pub fn path(&self) -> &Path { &self.path }
     pub fn user(&self) -> &str { &self.user }
     pub fn group(&self) -> &str { &self.group }