Add error stub

Cargo.toml

@@ -5,6 +5,7 @@ authors = ["Henry de Valence <hdevalence@hdevalence.ca>"]
 edition = "2018"
 
 [dependencies]
+thiserror = "1.0"
 blake2b_simd = "0.5"
 jubjub = { git = "https://github.com/zkcrypto/jubjub", rev = "e83f7d2bd136498a27f9d943fea635d8682bf2c6" }
 

src/error.rs

@@ -0,0 +1,9 @@
+use thiserror::Error;
+
+/// An error related to RedJubJub signatures.
+#[derive(Error, Debug)]
+pub enum Error {
+    /// This is a stub variant to check that thiserror derive works.
+    #[error("Stub error--  remove this.")]
+    StubError,
+}

src/lib.rs

@@ -1,13 +1,15 @@
 #![cfg_attr(feature = "nightly", feature(external_doc))]
 #![cfg_attr(feature = "nightly", doc(include = "../README.md"))]
+#![deny(missing_docs)]
 
 //! Docs require the `nightly` feature until RFC 1990 lands.
 
+mod error;
 mod public_key;
 mod secret_key;
 mod signature;
-mod error;
 
+pub use error::Error;
 
 #[cfg(test)]
 mod tests {