T8599: fail build on patch fail

[hedrok]

Change summary

When patch fails to apply exit with error instead of ignoring it.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe): enhance build system: fail on patch fail.

Related Task(s)

• https://vyos.dev/T8599

Related PR(s)

How to test / Smoketest result

Add failing patch, try to build. Result before this PR:

dpkg-source: info: applying 0004-does-not-apply.patch
patching file ospf6d/ospf6_auth_trailer.c
Hunk #1 succeeded at 534 (offset -19 lines).
Hunk #2 FAILED at 572.
1 out of 2 hunks FAILED
dpkg-source: info: the patch has fuzz which is not allowed, or is malformed
dpkg-source: info: if patch '0004-does-not-apply.patch' is correctly applied by quilt, use 'quilt refresh' to update it
dpkg-source: info: if the file is present in the unpacked source, make sure it is also present in the orig tarball
dpkg-source: info: restoring quilt backup files for 0004-does-not-apply.patch
dpkg-source: error: LC_ALL=C patch -t -F 0 -N -p1 -u -V never -E -b -B .pc/0004-does-not-apply.patch/ --reject-file=- < frr/debian/patches/0004-does-not-apply.patch subprocess returned exit status 1
dpkg-buildpackage: error: dpkg-source --before-build . subprocess returned exit status 2

Inside of build log - package builds successfully, it is extremely easy not to see this.

With PR:

dpkg-source: error: LC_ALL=C patch -t -F 0 -N -p1 -u -V never -E -b -B .pc/0004-does-not-apply.patch/ --reject-file=- < frr/debian/patches/0004-does-not-apply.patch subprocess returned exit status 1
dpkg-buildpackage: error: dpkg-source --before-build . subprocess returned exit status 2
Command 'sudo dpkg -i ../*.deb; dpkg-buildpackage -us -uc -tc -b -Ppkg.frr.rtrlib,pkg.frr.lua' returned non-zero exit status 2.
E: Source packages build failed, possibly patches problem

With failure.

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

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[github-actions]

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No issues in PR Title / Commit Title

[sever-sever]

The netfilter binaries cannot be built with this change, or it detected some issues with our netfilter patches/etc

dpkg-source: info: using options from pkg-libnftnl/debian/source/options: --extend-diff-ignore=(^|/)(compile|config\.sub|config\.guess|Makefile|configure|Makefile\.in|aclocal.m4|config.h.in|depcomp|INSTALL|install-sh|ltmain.sh|missing||libtool.m4|lt~obsolete.m4|ltoptions.m4|ltsugar.m4|ltversion.m4|.Po)
dpkg-source: error: can't build with source format '3.0 (quilt)': no upstream tarball found at ../libnftnl_1.2.6.orig.tar.{bz2,gz,lzma,xz}
dpkg-buildpackage: error: dpkg-source --tar-ignore=.git --tar-ignore=.github -b . subprocess returned exit status 2
Command 'dpkg-buildpackage -uc -us -tc -F --source-option=--tar-ignore=.git --source-option=--tar-ignore=.github' returned non-zero exit status 2.
E: Source packages build failed, possibly patches problem
vyos_bld@0878fc04fa6d:/vyos/work/tmp/build-bin-patch/vyos-build/scripts/package-build/netfilter$ 
vyos_bld@0878fc04fa6d:/vyos/work/tmp/build-bin-patch/vyos-build/scripts/package-build/netfilter$ 

Packages that cannot build after this change:

• ddclient
• dropbear
• ethtool
• isc-dhcp
• keepalived
• ndppd
• netfilter
• strongswan

[Copilot]

Pull request overview

Updates the package build helper to fail fast when dpkg-buildpackage (including dpkg-source patch application) errors, instead of continuing with a binaries-only build that can hide patch failures in logs.

Changes:

• Stop ignoring source package build failures and exit the script with an error.
• Update console output to surface the failure as an error.

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[Copilot]

This handler exits with status 1 for any dpkg-buildpackage failure, which can hide the underlying return code (e.returncode is often 2 for dpkg-source/patch failures). Consider exiting with the original return code (or re-raising and letting the top-level handle it) so CI/logs reflect the real failure reason.

Suggested change

	sys.exit(1)
	sys.exit(e.returncode if e.returncode is not None else 1)

[Copilot]

The message "Source packages build failed, possibly patches problem" will be printed for any failure of build_cmd (e.g., compile/test failures too), so it may be misleading. Recommend making the message generic (include repo_name/build_cmd), and/or only mention patches when the failure is specifically detected as a dpkg-source/patch application error.

Suggested change

	print("E: Source packages build failed, possibly patches problem")
	print(f'E: Source package build failed for "{repo_name}" while running: {build_cmd}')