imgtestlib: handle missing sources key in tests

Prevent a KeyError crash when accessing org.osbuild.curl for missing
sources.

Author: avitova

test/scripts/imgtestlib/core.py

@@ -428,7 +428,11 @@ def can_boot_test(manifest_fname, manifest_data, image_type, arch, distro, bluep
                   "FATAL: FIPS integrity test failed")
             return False
         # Note that this needs adjustment when we switch to librepo
-        urls = [src["url"] for src in manifest_data["sources"]["org.osbuild.curl"]["items"].values()]
+        curl_items = manifest_data.get("sources", {}).get("org.osbuild.curl", {}).get("items", {})
+        if not curl_items:
+            print(f"  not bootable: no org.osbuild.curl source in manifest {manifest_fname} ({arch} {image_type})")
+            return False
+        urls = [src["url"] for src in curl_items.values()]
         if not any("ssh-server" in url for url in urls):
             # This can happen e.g. when an image is build with the "minimal: true" customization.
             # We could use guestfs to inject keys, see PR#1995