openpgp: Fix Signature::get_issuer to return set of issuers.

  - A signature can contain multiple hints as to who created the
    signature.  Return all those hints to the caller.

  - Adapt all callers accordingly.

  - Fixes #264.

1 files changed, 3 insertions, 2 deletions

diff --git a/tool/src/commands/mod.rs b/tool/src/commands/mod.rs
index 6da5f56b..a7b76038 100644
--- a/tool/src/commands/mod.rs
+++ b/tool/src/commands/mod.rs
@@ -238,8 +238,9 @@ impl<'a> VHelper<'a> {
         use self::VerificationResult::*;
         for result in results {
             if let MissingKey { sig } = result {
-                let issuer = sig.get_issuer()
-                    .expect("missing key checksum has an issuer");
+                let issuer = sig.get_issuers().iter().nth(0)
+                    .expect("missing key checksum has an issuer")
+                    .to_string();
                 let what = match sig.level() {
                     0 => "checksum".into(),
                     n => format!("level {} notarizing checksum", n),