tests: isolate invalid unban CLI check

tests/static-checks.sh

@@ -10,7 +10,7 @@ find gateway prod-server ban-internal-server -type f -name '*.py' -exec \
 find ban-server -type f -name '*.php' -exec php -l {} \;
 find gateway prod-server common -type f -name '*.sh' -exec sh -n {} \;
 
-if python3 gateway/usr/share/eterban/unban.py >/dev/null 2>&1; then
+if printf '%s\n' '[Settings]' | python3 -c 'from pathlib import Path; p = Path("gateway/usr/share/eterban/unban.py"); code = p.read_text().replace("/etc/eterban/settings.ini", "/proc/self/fd/0"); exec(compile(code, str(p), "exec"))' >/dev/null 2>&1; then
     echo 'unban.py without an IP must fail' >&2
     exit 1
 fi