Check f1-circuits' service code before a change merges into what the mesh builds (hq ADR 0237)

The repository's layer of the mesh's merge check (mesh/repo-check): every Python file
the image ships, parsed; what cannot run is said.

merge-check.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+# mesh-check-toolchain: go
+#
+# f1-circuits' own check (novox/hq ADR 0237): the second layer of a pull request's merge check,
+# `mesh/repo-check`, run by the build seat in the mesh's Go toolchain, which carries Python for the merge
+# checks that need it. The gate — the manifest through the controller the mesh runs, every machine
+# composed with it — is the build seat's first layer (`mesh/merge-gate`), run because the mesh's module
+# graph builds f1-circuits from this branch.
+#
+# What the image ships, compiled before the merge: every Python file the service's image copies, and the
+# models it imports.
+#
+# **Said, never passed silently**: the service's dependencies (service/requirements.txt) are the image's to
+# install, so the service is not started, and the repository has no tests.
+set -eu
+
+# Parsed, not compiled to files: a check leaves the tree as it found it.
+find cdn-api.py circuits_service.py ergast_service.py posters_service.py models -name '*.py' -print0 |
+	xargs -0 python3 -c 'import ast, sys
+for f in sys.argv[1:]:
+    ast.parse(open(f, encoding="utf-8").read(), f)
+print(len(sys.argv) - 1, "Python file(s) parse")'
+echo "NOT RUN HERE: the service (its dependencies are the image's to install); the repository has no tests"