python: add vendor.py utility

This is a teeny-tiny script that just downloads any packages we want to
vendor from PyPI and stores them in qemu.git/python/wheels/. If I'm hit
by a meteor, it'll be easy to replicate what I have done in order to
udpate the vendored source.

We don't really care which python runs it; it exists as a meta-utility
with no external dependencies and we won't package or install it. It
will be monitored by the linters/type checkers, though; so it's
guaranteed safe on python 3.6+.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20230511035435.734312-15-jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

python/scripts/vendor.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+"""
+vendor - QEMU python vendoring utility
+
+usage: vendor [-h]
+
+QEMU python vendoring utility
+
+options:
+  -h, --help  show this help message and exit
+"""
+
+# Copyright (C) 2023 Red Hat, Inc.
+#
+# Authors:
+#  John Snow <jsnow@redhat.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2 or
+# later. See the COPYING file in the top-level directory.
+
+import argparse
+import os
+from pathlib import Path
+import subprocess
+import sys
+import tempfile
+
+
+def main() -> int:
+    """Run the vendoring utility. See module-level docstring."""
+    loud = False
+    if os.environ.get("DEBUG") or os.environ.get("V"):
+        loud = True
+
+    # No options or anything for now, but I guess
+    # you'll figure that out when you run --help.
+    parser = argparse.ArgumentParser(
+        prog="vendor",
+        description="QEMU python vendoring utility",
+    )
+    parser.parse_args()
+
+    packages = {
+        "meson==0.61.5":
+        "58c2ddb5f885da0e929f15d89f38d8a7d97f981f56815bcba008414f8511f59a",
+    }
+
+    vendor_dir = Path(__file__, "..", "..", "wheels").resolve()
+
+    with tempfile.NamedTemporaryFile(mode="w", encoding="utf-8") as file:
+        for dep_spec, checksum in packages.items():
+            file.write(f"{dep_spec} --hash=sha256:{checksum}")
+        file.flush()
+
+        cli_args = [
+            "pip",
+            "download",
+            "--dest",
+            str(vendor_dir),
+            "--require-hashes",
+            "-r",
+            file.name,
+        ]
+        if loud:
+            cli_args.append("-v")
+
+        print(" ".join(cli_args))
+        subprocess.run(cli_args, check=True)
+
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())