Fix YumPackageManager false positive when package name contains "errno" by yashnap · Pull Request #393 · Azure/LinuxPatchExtension

yashnap · 2026-10-06T22:19:33Z

What's happening: RHEL 9.8 VMs log ERROR:[YPM] Customer Environment Error: Not a known error , but patch assessment is actually succeeding ( TaskStatus=succeeded , updates reported correctly).

What customer sees:

Root cause:
YPM's error handling checks the package manager output for the strings "Error" or "Errno". One of the packages returned by the command is perl-Errno, which contains the substring "Errno". As a result, a normal check-update or list installed output is incorrectly treated as an error. The output does not match any known error pattern, so YPM logs:
Customer Environment Error: Not a known error...
This is a false positive caused by a package name and not an actual customer environment issue.

Fix : Update the Exception block to exclude the package when checking for errors.

Copilot

Copilot review overview

🟡 Changes recommended

The exclusion can hide genuine errors when the output also contains perl-Errno, and the new test does not detect the original behavior.

Review effort: Balanced
Findings: 2

Open (2)

Avoid suppressing unrelated errors when perl-Errno appears · New
Test does not detect regression in known-issue handling · New

What changed in this PR

Prevents perl-Errno package names from triggering Yum error mitigation.

Changes:

Excludes perl-Errno from error detection.
Adds a regression test for the false positive.

File	Description
`src/core/src/package_managers/YumPackageManager.py`	Adjusts Yum error detection.
`src/core/tests/Test_YumPackageManager.py`	Adds regression coverage.

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codecov · 2026-10-06T22:31:59Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.06%. Comparing base (3066008) to head (8851d54).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #393      +/-   ##
==========================================
+ Coverage   95.03%   95.06%   +0.03%     
==========================================
  Files         113      113              
  Lines       21994    22013      +19     
==========================================
+ Hits        20901    20926      +25     
+ Misses       1093     1087       -6

Flag	Coverage Δ
python27	`95.03% <100.00%> (+<0.01%)`	⬆️
python312	`95.03% <100.00%> (+<0.01%)`	⬆️

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Rajasi Rane (rane-rajasi)

Comments inline.

Rajasi Rane (rane-rajasi) · 2026-10-07T00:49:04Z

+        self.assertTrue(package_manager)
+
+        mitigation_attempted = {'called': False}
+        def record_call(output):


Define mock functions outside similar to other test structures

Rajasi Rane (rane-rajasi) · 2026-10-07T00:50:17Z

+        package_manager = self.container.get('package_manager')
+        self.assertTrue(package_manager)
+
+        package_manager.check_known_issues_and_attempt_fix = lambda output: self.fail("perl-Errno must not enter error mitigation")


Review whether we use lambda functions, IIRC we use mock functions.

Rajasi Rane (rane-rajasi)

Comments inline.

Rajasi Rane (rane-rajasi) · 2026-10-08T13:48:21Z

        return ['Red Hat Enterprise Linux Server', '8', 'Ootpa']
+
+    def mock_check_known_issues_and_attempt_fix_record_call(self, output):
+        self.check_known_issues_and_attempt_fix_called = True


This is not a class level variable i.e. ideally defined in init() or for the purpose of UTs, defined in setUp()

Removed the mock since none of the added tests now uses it

Rajasi Rane (rane-rajasi) · 2026-10-08T13:51:33Z

+
+        package_manager.check_known_issues_and_attempt_fix = backup_check_known_issues_and_attempt_fix
+
+        self.assertTrue(self.check_known_issues_and_attempt_fix_called)


Primary assert should not be on whether a mock function is called, this can be an additional assert. However, the primary one should always be on the expected outcome, say the status reported, etc

Updated the assert

Rajasi Rane (rane-rajasi) · 2026-10-08T13:56:47Z

+
+        self.check_known_issues_and_attempt_fix_called = False
+        backup_check_known_issues_and_attempt_fix = package_manager.check_known_issues_and_attempt_fix
+        package_manager.check_known_issues_and_attempt_fix = self.mock_check_known_issues_and_attempt_fix_record_call


Why mock check_known_issues_and_attempt_fix () in both of these tests? It is simply using the error message to verify against known errors and attempts a fix if a match is found. Which here will not match, so no fix is attempted. Non mocking will actually test the complete functionality

Removed the mock usage.

Rajasi Rane (rane-rajasi) · 2026-10-08T13:58:41Z

+
+        self.check_known_issues_and_attempt_fix_called = False
+        backup_check_known_issues_and_attempt_fix = package_manager.check_known_issues_and_attempt_fix
+        package_manager.check_known_issues_and_attempt_fix = self.mock_check_known_issues_and_attempt_fix_record_call


Same question on why this is mocked? There is also an existing test with the similar error (barring perl-Errno) which runs without a mock: test_auto_issue_mitigation_when_retries_are_exhausted_raise_exception_disabled()

I didnt notice the other test. I've updated to have the same pattern and not use mock

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Copilot AI balanced review requested due to automatic review settings October 6, 2026 22:19

yashnap requested review from Koshy John (kjohn-msft), Mike Richmond (mirichmo) and Rajasi Rane (rane-rajasi) as code owners October 6, 2026 22:19

github-actions Bot requested review from GAURAVRAMRAKHYANI, SathishMSFT, Michelle McDaniel (michellemcdaniel) and nikhim-um October 6, 2026 22:19

Copilot started reviewing on behalf of yashnap October 6, 2026 22:21 View session

Copilot AI reviewed Oct 6, 2026

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Comment thread src/core/src/package_managers/YumPackageManager.py Outdated

Comment thread src/core/tests/Test_YumPackageManager.py

Fix False positive

2808689

yashnap force-pushed the icm_fix branch from af33e35 to 2808689 Compare October 6, 2026 22:27

Koshy John (kjohn-msft) added the bug Something isn't working label Oct 6, 2026

Address copilot suggestion

0bec50f

Koshy John (kjohn-msft) previously approved these changes Oct 6, 2026

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Rajasi Rane (rane-rajasi) requested changes Oct 7, 2026

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Address code review

2a9657d

yashnap dismissed Koshy John (kjohn-msft)’s stale review via 2a9657d October 7, 2026 16:08

Koshy John (kjohn-msft) previously approved these changes Oct 7, 2026

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Rajasi Rane (rane-rajasi) requested changes Oct 8, 2026

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Fix UT

510c54d

yashnap dismissed Koshy John (kjohn-msft)’s stale review via 510c54d October 8, 2026 17:10

github-code-quality Bot found potential problems Oct 8, 2026

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Comment thread src/core/tests/Test_YumPackageManager.py Fixed

Copilot suggestion

8851d54

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Koshy John (kjohn-msft) approved these changes Oct 8, 2026

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Michelle McDaniel (michellemcdaniel) approved these changes Oct 8, 2026

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		package_manager.check_known_issues_and_attempt_fix = backup_check_known_issues_and_attempt_fix

		self.assertTrue(self.check_known_issues_and_attempt_fix_called)

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yashnap commented Oct 6, 2026

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codecov Bot commented Oct 6, 2026 •

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