IT Unstable case TestSumAvg

[aytrack]

Bug Report

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in ci https://ci.pingcap.net/blue/organizations/jenkins/tidb_ghpr_coverage/detail/tidb_ghpr_coverage/1416/pipeline/

2021-12-01T02:26:54.531Z] --- FAIL: TestSumAvg (1.39s)
[2021-12-01T02:26:54.531Z]     dbtestkit.go:81: 
[2021-12-01T02:26:54.531Z]         	Error Trace:	dbtestkit.go:81
[2021-12-01T02:26:54.531Z]         	            				server_test.go:1864
[2021-12-01T02:26:54.531Z]         	            				server_test.go:117
[2021-12-01T02:26:54.531Z]         	            				server_test.go:1853
[2021-12-01T02:26:54.531Z]         	            				tidb_test.go:1114
[2021-12-01T02:26:54.531Z]         	Error:      	Received unexpected error:
[2021-12-01T02:26:54.531Z]         	            	No Pem data found, data: ��#28000Access denied for user 'root'@'127.0.0.1' (using password: YES)
[2021-12-01T02:26:54.531Z]         	Test:       	TestSumAvg
[2021-12-01T02:26:54.531Z]         	Messages:   	sql:select avg(a), avg(b), avg(c) from sumavg, args:[]

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[hawkingrei]

Closed by #30306

[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.

[hawkingrei]

we can re-open it if the error happens again.