Test that loading a non existent configuration file returns an IO error

src/config.rs

@@ -7,7 +7,7 @@ use reqwest::Url;
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 use std::{
     collections::{HashMap, HashSet},
-    fmt,
+    fmt, io,
     ops::Deref,
     path::{Path, PathBuf},
     sync::Arc,
@@ -158,8 +158,10 @@ impl Configuration {
 }
 
 /// An error that can occur when interacting with a [`Configuration`].
-#[derive(Debug, PartialEq, thiserror::Error)]
+#[derive(Debug, thiserror::Error)]
 pub enum Error {
+    #[error("{0}")]
+    Io(#[from] io::Error),
     #[error("{0}")]
     SyntaxError(figment::Error),
     #[error("missing sources {0}")]
@@ -289,6 +291,18 @@ mod tests {
         });
     }
 
+    #[rstest]
+    fn loading_non_existent_configuration_returns_io_error(config_path: PathBuf) {
+        figment::Jail::expect_with(|_| {
+            let err = Configuration::load(&config_path, None).unwrap_err();
+            if let Error::Io(_) = err {
+                Ok(())
+            } else {
+                Err("Did not return expected error".into())
+            }
+        });
+    }
+
     /// Loading configuration missing sources returns an appropriate error.
     #[rstest]
     #[case(