fix: call error_handler for SessionError (#557)

Closes: #546

src/crawlee/basic_crawler/_basic_crawler.py

@@ -851,6 +851,9 @@ async def __run_task_function(self) -> None:
             if not crawling_context.session:
                 raise RuntimeError('SessionError raised in a crawling context without a session') from session_error
 
+            if self._error_handler:
+                await self._error_handler(crawling_context, session_error)
+
             if self._should_retry_request(crawling_context, session_error):
                 self._logger.warning('Encountered a session error, rotating session and retrying')
 

tests/unit/basic_crawler/test_basic_crawler.py

@@ -9,7 +9,7 @@
 from datetime import timedelta
 from pathlib import Path
 from typing import TYPE_CHECKING, Any
-from unittest.mock import Mock
+from unittest.mock import AsyncMock, Mock
 
 import httpx
 import pytest
@@ -189,6 +189,26 @@ async def error_handler(context: BasicCrawlingContext, error: Exception) -> Requ
     assert calls[1][2] == 1
 
 
+async def test_calls_error_handler_for_sesion_errors() -> None:
+    crawler = BasicCrawler(
+        max_session_rotations=1,
+    )
+
+    @crawler.router.default_handler
+    async def handler(context: BasicCrawlingContext) -> None:
+        raise SessionError('Arbitrary session error for testing purposes')
+
+    error_handler_mock = AsyncMock()
+
+    @crawler.error_handler
+    async def error_handler(context: BasicCrawlingContext, error: Exception) -> None:
+        await error_handler_mock(context, error)
+
+    await crawler.run(['https://crawlee.dev'])
+
+    assert error_handler_mock.call_count == 1
+
+
 async def test_handles_error_in_error_handler() -> None:
     crawler = BasicCrawler(
         request_provider=RequestList(['http://a.com/', 'http://b.com/', 'http://c.com/']),