Intermediate commit

app/services/domains/arxiv/errors.py

@@ -0,0 +1,13 @@
+from __future__ import annotations
+
+
+class ArxivRateLimitError(Exception):
+    """arXiv returned 429 or cooldown is active."""
+
+
+class ArxivClientValidationError(ValueError):
+    """arXiv client inputs are invalid."""
+
+
+class ArxivParseError(ValueError):
+    """arXiv API payload could not be parsed."""