Add "No such release" error variant

src/lib.rs

@@ -16,6 +16,7 @@ pub enum Error {
     WrappedReqwestErr(reqwest::Error),
     MissingAuthToken,
     NoSuchFile, // for release attachment 'file exists' pre-check.
+    NoSuchRelease,
     ApiErrorMessage(ApiError),
 }
 

src/main.rs

@@ -88,6 +88,7 @@ async fn main() -> Result<(), gt_tools::Error> {
                 .await?;
             } else {
                 println!("ERR: Couldn't find a release matching the tag \"{tag_name}\".");
+                return Err(gt_tools::Error::NoSuchRelease);
             }
         }
     }