Relative to absolute, if needed

georss_download.py

 import xml.etree.ElementTree as ET
 from datetime import datetime
+from urllib.parse import urljoin
 
 from citygml_download import TMP_DIR, Bundesland, download_file
 from zipfile_download import ZipFile
@@ -23,8 +24,8 @@ def parse_atom_georss(bundesland: Bundesland) -> list[ZipFile]:
         raise ValueError("No date has been found")
     source_date = datetime.strptime(updated_date, "%Y-%m-%dT%H:%M:%SZ")
     for file_elem in root.findall("atom:entry/atom:link", ns):
-        # FIXME: href can be relative too. To what?
         href = file_elem.attrib["href"]
+        href = urljoin(bundesland.source, href)
         # TODO: Check if source_date is specified for each ZipFile
         if href.endswith(".zip"):
             zip_files.append(