sq: Improve error message for key userid add.

  - To add a userid to a key, private key material is needed.

  - State this explicitly in the error message.

  - Fixes #952.

1 files changed, 3 insertions, 1 deletions

diff --git a/sq/src/commands/key.rs b/sq/src/commands/key.rs
index f6f8b729..d428ceb0 100644
--- a/sq/src/commands/key.rs
+++ b/sq/src/commands/key.rs
@@ -340,7 +340,9 @@ fn userid_add(config: Config, command: sq_cli::key::UseridAddCommand) -> Result<
     // If a password is needed to use the key, the user will be prompted.
     let pk = get_primary_keys(&[key.clone()], &config.policy,
                               command.private_key_store.as_deref(),
-                              creation_time, None)?;
+                              creation_time, None);
+
+    let pk = pk.context("Adding a User ID requires the private key")?;
 
     assert_eq!(pk.len(), 1, "Expect exactly one result from get_primary_keys()");
     let mut pk = pk.into_iter().next().unwrap();