Error prompt not accurate when using lightning local backend to import data to TiDB 3.0.x (not support local backend)

[fubinzh]

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

• Use lightning 5.1 / 4.0 / 3.0 to import data to TiDB 3.0.17, and lightning backup set to local.

2. What did you expect to see?

• Lightning error prompt should be accurate and meaningful

3. What did you see instead?

• The error prompt only says that TiDB version too old, it doesn't say anything about local backend not supported by the target TiDB (3.0.x)

[root@CentOS76_VM 20G]# tiup tidb-lightning:v5.1.0 -config lightning.toml
Starting component tidb-lightning: /root/.tiup/components/tidb-lightning/v5.1.0/tidb-lightning -config lightning.toml
Verbose debug logs will be written to tidb-lightning.log

+---+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| # | CHECK ITEM | TYPE | PASSED |
+---+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 1 | cluster available check failed: TiDB version too old, required to be in [4.0.0, 6.0.0), found '3.0.17': [BR:Common:ErrVersionMisma | critical | false |
| | tch]version mismatch | | |
+---+------------------------------------------------------------------------------------------------------------------------------------+
...
1 critical check failed
Error: lightning pre check failed.please fix the check item and make check passed or set --check-requirement=false to avoid this check
tidb lightning encountered error: lightning pre check failed.please fix the check item and make check passed or set --check-requirement=false to avoid this check
Error: run /root/.tiup/components/tidb-lightning/v5.1.0/tidb-lightning (wd:/root/.tiup/data/SdCFxWu) failed: exit status 1

[root@CentOS76_VM 20G]# tiup tidb-lightning:v4.0.14 -config lightning.toml
Starting component tidb-lightning: /root/.tiup/components/tidb-lightning/v4.0.14/tidb-lightning -config lightning.toml
Verbose debug logs will be written to tidb-lightning.log

Error: TiDB version too old, required to be in [4.0.0, 5.0.0), found '3.0.17': [BR:Common:ErrVersionMismatch]version mismatch
tidb lightning encountered error: TiDB version too old, required to be in [4.0.0, 5.0.0), found '3.0.17': [BR:Common:ErrVersionMismatch]version mismatch
Error: run /root/.tiup/components/tidb-lightning/v4.0.14/tidb-lightning (wd:/root/.tiup/data/SdCGXlX) failed: exit status 1

root@CentOS76_VM v3.0.17]# ./tidb-lightning -config /minio/fubin/dbgen/20G/lightning.toml
Verbose debug logs will be written to /tmp/lightning.log.2021-07-15T10.47.34+0800.

[2021/07/15 10:47:34.867 +08:00] [INFO] [client.go:149] ["[pd] create pd client with endpoints"] [pd-address="[172.16.5.211:2379]"]
[2021/07/15 10:47:34.871 +08:00] [INFO] [base_client.go:242] ["[pd] switch leader"] [new-leader=http://172.16.5.211:2379] [old-leader=]
[2021/07/15 10:47:34.871 +08:00] [INFO] [base_client.go:92] ["[pd] init cluster id"] [cluster-id=6984706836438984534]
Error: TiDB version too old, expected '>=4.0.0', found '3.0.17'
tidb lightning encountered error: TiDB version too old, expected '>=4.0.0', found '3.0.17'
[root@CentOS76_VM v3.0.17]# ./tidb-lightning -V
Release Version: v3.0.17
Git Commit Hash: 4af19d5
Git Branch: HEAD
UTC Build Time: 2020-08-03 06:31:58
Go Version: go version go1.13 linux/amd64

4. What version of BR and TiDB/TiKV/PD are you using?

tidb-lightning: 5.x, 4.x, 3.x

5. Operation logs

   • Please upload br.log for BR if possible
   • Please upload tidb-lightning.log for TiDB-Lightning if possible
   • Please upload tikv-importer.log from TiKV-Importer if possible
   • Other interesting logs

6. Configuration of the cluster and the task

   • tidb-lightning.toml for TiDB-Lightning if possible
   • tikv-importer.toml for TiKV-Importer if possible
   • topology.yml if deployed by TiUP

7. Screenshot/exported-PDF of Grafana dashboard or metrics' graph in Prometheus if possible

[sleepymole]

This issue can be changed to an enhancement.