get_tenure_raw error message upgrade

signer/src/error.rs

@@ -114,6 +114,10 @@ pub enum Error {
     #[error("observed a tenure identified by a StacksBlockId with with no blocks")]
     EmptyStacksTenure,
 
+    /// This should never happen
+    #[error("get_tenure_raw returned unexpected responce: {0}. Expected: {1}")]
+    GetTenureRawMismatch(StacksBlockId, StacksBlockId),
+
     /// Received an error in call to estimatesmartfee RPC call
     #[error("failed to get fee estimate from bitcoin-core for target {1}. {0}")]
     EstimateSmartFee(#[source] bitcoincore_rpc::Error, u16),

signer/src/stacks/api.rs

@@ -810,7 +810,15 @@ impl StacksClient {
             // The first block in the GET /v3/tenures/<block-id> response
             // is always the block related to the given <block-id>. But we
             // already have that block, so we can skip adding it again.
-            debug_assert_eq!(blocks.first().map(|b| b.block_id()), Some(last_block_id));
+
+            if let Some(received_id) = blocks.first().map(|b| b.block_id()) {
+                if received_id != last_block_id {
+                    return Err(Error::GetTenureRawMismatch(received_id, last_block_id));
+                }
+            } else {
+                return Err(Error::EmptyStacksTenure);
+            }
+
             tenure_blocks.extend(blocks.into_iter().skip(1))
         }