scripts: Move download-overrides.py to coreos-assembler/main/src

This script will be now used in cosa. It makes more sense to move it,
to avoid fetching it from the automation repo.

See: coreos/fedora-coreos-tracker#1185

See: coreos#3510

src/download-overrides.py

@@ -0,0 +1,71 @@
+#!/usr/bin/python3
+
+import dnf.subject
+import hawkey
+import os
+import yaml
+import subprocess
+import sys
+
+arch = os.uname().machine
+
+# this was partially copied from coreos-koji-tagger
+def get_rpminfo(string: str) -> str:
+    form = hawkey.FORM_NEVRA
+
+    # get a hawkey.Subject object for the string
+    subject = dnf.subject.Subject(string)  # returns hawkey.Subject
+
+    # get a list of hawkey.NEVRA objects that are the possibilities
+    nevras = subject.get_nevra_possibilities(forms=form)
+
+    # return the first hawkey.NEVRA item in the list of possibilities
+    rpminfo = nevras[0]
+    return rpminfo
+
+def is_override_lockfile(filename: str) -> bool:
+    return (filename == "manifest-lock.overrides.yaml" or
+            filename == f'manifest-lock.overrides.{arch}.yaml')
+
+def assert_epochs_match(overrides_epoch: int, rpmfile_epoch: str):
+    # normalize the input into a string
+    if overrides_epoch is None:
+       normalized_overrides_epoch = '(none)' # matches rpm -qp --queryformat='%{E}'
+    else:
+       normalized_overrides_epoch = str(overrides_epoch)
+    if  normalized_overrides_epoch != rpmfile_epoch:
+        raise Exception(f"Epoch mismatch between downloaded rpm ({rpmfile_epoch})"
+                        f" and overrides file entry ({overrides_epoch})")
+
+assert os.path.isdir("builds"), "Missing builds/ dir; is this a cosa workdir?"
+
+rpms = set()
+os.makedirs('overrides/rpm', exist_ok=True)
+for filename in os.listdir(os.path.join("src/config")):
+    if is_override_lockfile(filename):
+        with open(f'src/config/{filename}') as f:
+            lockfile = yaml.safe_load(f)
+        if lockfile is None or 'packages' not in lockfile:
+            continue
+        for pkg, pkgobj in lockfile['packages'].items():
+            if 'evr' in pkgobj:
+                rpminfo = get_rpminfo(f"{pkg}-{pkgobj['evr']}.{arch}")
+            else:
+                rpminfo = get_rpminfo(f"{pkg}-{pkgobj['evra']}")
+            rpmnvra = f"{rpminfo.name}-{rpminfo.version}-{rpminfo.release}.{rpminfo.arch}"
+            rpms.add(rpmnvra)
+            subprocess.check_call(['koji', 'download-build', '--rpm', rpmnvra], cwd='overrides/rpm')
+            # Make sure the epoch matches what was in the overrides file
+            # otherwise we can get errors: https://github.com/coreos/fedora-coreos-config/pull/293
+            cp = subprocess.run(['rpm', '-qp', '--queryformat', '%{E}', f'{rpmnvra}.rpm'],
+                                  check=True,
+                                  capture_output=True,
+                                  cwd='overrides/rpm')
+            rpmfile_epoch = cp.stdout.decode('utf-8')
+            assert_epochs_match(rpminfo.epoch, rpmfile_epoch)
+
+if not rpms:
+    print("No overrides; exiting.")
+else:
+    for rpm in rpms:
+        print(f'Downloaded {rpm} to overrides dir')