Added helper error if the remote URL

doesn't return a valid CSV blocklist.
Updated sample config to use valid raw github URL.

bin/fediblock_sync.py

@@ -319,7 +319,11 @@ def save_blocklist_to_file(blocklist: list[dict], filepath: str):
     @param blocklist: A dictionary of block definitions, keyed by domain
     @param filepath: The path to the file the list should be saved in.
     """
-    blocklist = sorted(blocklist, key=lambda x: x['domain'])
+    try:
+        blocklist = sorted(blocklist, key=lambda x: x['domain'])
+    except KeyError:
+        log.error("Field 'domain' not found in blocklist. Are you sure the URLs are correct?")
+        log.debug(f"blocklist is: {blocklist}")
 
     fieldnames = ['domain', 'severity', 'private_comment', 'public_comment', 'reject_media', 'reject_reports', 'obfuscate']
     with open(filepath, "w") as fp:

etc/sample.fediblockhole.conf.toml

@@ -8,7 +8,7 @@ blocklist_instance_sources = [
 # List of URLs to read csv blocklists from
 blocklist_url_sources = [
     'file:///etc/fediblockhole/blocklist-01.csv',
-    'https://github.com/fediblockhole/samples/demo-blocklist-01.csv',
+    'https://raw.githubusercontent.com/eigenmagic/fediblockhole/main/samples/demo-blocklist-01.csv',
 ]
 
 # List of instances to write blocklist to