CLSA-2026-1777946871 python: Fix of CVE-2026-4519

CVE-2026-4519: reject leading dashes in webbrowser URLs that could be treated as command-line options by external browsers; also close a %action-substitution bypass of the check in UnixBrowser.open...

CLSA-2026-1777946712 python: Fix of CVE-2026-4519

CVE-2026-4519: reject leading dashes in webbrowser URLs that could be treated as command-line options by external browsers; also close a %action-substitution bypass of the check in UnixBrowser.open...