consensus: reduce "Error attempting to add vote" message severity (Er… (#3871)

* consensus: reduce "Error attempting to add vote" message severity (Error -> Info)

Fixes #3839

* add missing changelog entry

CHANGELOG_PENDING.md

@@ -19,5 +19,8 @@ program](https://hackerone.com/tendermint).
 
 ### IMPROVEMENTS:
 
+- [consensus] \#3839 Reduce "Error attempting to add vote" message severity (Error -> Info)
+
 ### BUG FIXES:
+
 - [config] \#3868 move misplaced `max_msg_bytes` into mempool section

consensus/state.go

@@ -1518,9 +1518,11 @@ func (cs *ConsensusState) tryAddVote(vote *types.Vote, peerID p2p.ID) (bool, err
 			cs.evpool.AddEvidence(voteErr.DuplicateVoteEvidence)
 			return added, err
 		} else {
-			// Probably an invalid signature / Bad peer.
-			// Seems this can also err sometimes with "Unexpected step" - perhaps not from a bad peer ?
-			cs.Logger.Error("Error attempting to add vote", "err", err)
+			// Either
+			// 1) bad peer OR
+			// 2) not a bad peer? this can also err sometimes with "Unexpected step" OR
+			// 3) tmkms use with multiple validators connecting to a single tmkms instance (https://github.com/tendermint/tendermint/issues/3839).
+			cs.Logger.Info("Error attempting to add vote", "err", err)
 			return added, ErrAddingVote
 		}
 	}