Fix error message when altering a non-exist user (apache#16126)

Author: jt2594838

integration-test/src/test/java/org/apache/iotdb/db/it/auth/IoTDBRelationalAuthIT.java

@@ -44,6 +44,8 @@
 import java.util.HashSet;
 import java.util.Set;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 @RunWith(IoTDBTestRunner.class)
 @Category({TableLocalStandaloneIT.class, TableClusterIT.class})
 public class IoTDBRelationalAuthIT {
@@ -620,4 +622,16 @@ public void testCreateUserAndRole() throws SQLException {
       Assert.fail();
     }
   }
+
+  @Test
+  public void testAlterNonExistingUser() throws SQLException {
+    try (Connection adminCon = EnvFactory.getEnv().getConnection(BaseEnv.TABLE_SQL_DIALECT);
+        Statement adminStmt = adminCon.createStatement()) {
+      try {
+        adminStmt.execute("ALTER USER nonExist SET PASSWORD 'asdfer1124566'");
+      } catch (SQLException e) {
+        assertEquals("701: User nonExist not found", e.getMessage());
+      }
+    }
+  }
 }

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/auth/ClusterAuthorityFetcher.java

@@ -540,10 +540,10 @@ public User getUser(String userName) {
       } catch (ClientManagerException | TException e) {
         LOGGER.error(CONNECTERROR);
       }
-      user = cacheUser(permissionInfoResp);
       if (permissionInfoResp != null
           && permissionInfoResp.getStatus().getCode()
               == TSStatusCode.SUCCESS_STATUS.getStatusCode()) {
+        user = cacheUser(permissionInfoResp);
         if (acceptCache) {
           iAuthorCache.putUserCache(userName, user);
         }