ci: add a no-python3 job reproducing the Debian buildd chroot

GitHub runners ship python3, so every make-check job exercised the
python3-present path and the local-server tests never skipped. The Debian
buildds build in a minimal chroot with no python3, where those tests must
SKIP (exit 77) -- and 28_local-pause failed there instead, FTBFS on every
arch for 3.49.10-1, invisible to CI.

Add a job that builds, removes python3, and runs make check, so the skip
path is exercised on every PR. Verified to fail on the pre-fix tree and pass
after.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Xavier Roche <roche@httrack.com>

debian/changelog

@@ -1,12 +1,3 @@
-httrack (3.49.10-2) unstable; urgency=medium
-
-  * Fix FTBFS: tests/28_local-pause failed instead of skipping when python3 is
-    absent (the local-server tests need python3, which the buildds lack). Add
-    patches/skip-local-pause-test-without-python3.patch to guard the test on
-    python3 up front, like its siblings, so it skips cleanly.
-
- -- Xavier Roche <xavier@debian.org>  Sun, 28 Jun 2026 20:18:46 +0200
-
 httrack (3.49.10-1) unstable; urgency=medium
 
   * New upstream release: new download-pacing and URL-handling options plus a

debian/patches/series

@@ -1 +0,0 @@
-skip-local-pause-test-without-python3.patch

debian/patches/skip-local-pause-test-without-python3.patch

@@ -1,29 +0,0 @@
-Description: skip 28_local-pause when python3 is absent (fixes FTBFS on buildds)
- The local-server tests skip (exit 77) when python3 is missing, but
- 28_local-pause wrapped local-crawl.sh in a command substitution that swallowed
- that skip. On the python3-less buildd chroot the test then ran serverless, both
- crawls finished in 0s, and the 0s delta was reported as a failure. Guard the
- test on python3 up front, like its siblings, so it skips cleanly.
-Author: Xavier Roche <roche@httrack.com>
-Origin: upstream, https://github.com/xroche/httrack/pull/445
-Applied-Upstream: https://github.com/xroche/httrack/commit/45279d7
-Forwarded: not-needed
-Last-Update: 2026-06-28
-diff --git a/tests/28_local-pause.test b/tests/28_local-pause.test
-index 8505a75..add95d1 100755
---- a/tests/28_local-pause.test
-+++ b/tests/28_local-pause.test
-@@ -9,6 +9,13 @@ set -e
- 
- : "${top_srcdir:=..}"
- 
-+# python3 runs the local server (mirror local-crawl.sh); skip when absent, else
-+# run() swallows its exit-77 and the serverless 0s/0s crawl looks like a fail.
-+command -v python3 >/dev/null || {
-+    echo "python3 not found; skipping local crawl tests"
-+    exit 77
-+}
-+
- run() { # echoes the wall-clock seconds of one crawl
-     local t0 t1
-     t0=$(date +%s)