3291 follow-up (#3323)

* changelog: use issue number instead of PR number

* follow up to #3291

- rpc/test/helpers.go add StopTendermint(node) func
- remove ensureDir(filepath.Dir(walFile), 0700)
- mempool/mempool_test.go add type cleanupFunc func()

* cmd/show_validator: wrap err to make it more clear

consensus/common_test.go

@@ -37,7 +37,8 @@ const (
 	testSubscriber = "test-client"
 )
 
-// A cleanupFunc cleans up any config / test files created for a particular test.
+// A cleanupFunc cleans up any config / test files created for a particular
+// test.
 type cleanupFunc func()
 
 // genesis, chain_id, priv_val