Unstable CI test TestDBNameEscape

[tiancaiamao]

Bug Report

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[2021-12-01T02:09:48.585Z] --- FAIL: TestDBNameEscape (1.69s)
[2021-12-01T02:09:48.585Z]     dbtestkit.go:72:
[2021-12-01T02:09:48.585Z]              Error Trace:    dbtestkit.go:72
[2021-12-01T02:09:48.585Z]                                                      server_test.go:1638
[2021-12-01T02:09:48.585Z]                                                      server_test.go:117
[2021-12-01T02:09:48.585Z]                                                      server_test.go:1635
[2021-12-01T02:09:48.585Z]                                                      tidb_test.go:220
[2021-12-01T02:09:48.585Z]              Error:          Received unexpected error:
[2021-12-01T02:09:48.585Z]                              No Pem data found, data: ^U^D#28000Access denied for user 'root'@'127.0.0.1' (using password: YES)
[2021-12-01T02:09:48.585Z]              Test:           TestDBNameEscape
[2021-12-01T02:09:48.585Z]              Messages:       sql:USE mysql;, args:[]

1. Minimal reproduce step (Required)

Found in CI https://ci.pingcap.net/blue/organizations/jenkins/tidb_ghpr_check_2/detail/tidb_ghpr_check_2/49324/pipeline
#30290

2. What did you expect to see? (Required)

CI success

3. What did you see instead (Required)

Fail

4. What is your TiDB version? (Required)

commit a046014 (HEAD -> master, origin/master, origin/HEAD)
Author: Song Gao disxiaofei@163.com
Date: Wed Dec 1 11:23:53 2021 +0800

planner: Add trace for proj elimination rule (#30275)

[tiancaiamao]

This one looks like #30249

[bb7133]

Very likely that this issue can be closed by #30306, I will close it for now.

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.