Fix #2549: Improve error handling for Ollama connection errors

Co-Authored-By: Joe Moura <joao@crewai.com>

tests/test_ollama_connection.py

@@ -0,0 +1,17 @@
+import pytest
+from unittest.mock import patch, MagicMock
+from crewai.llm import LLM
+from crewai.utilities.exceptions.ollama_connection_exception import OllamaConnectionException
+
+class TestOllamaConnection:
+    def test_ollama_connection_error(self):
+        with patch('litellm.completion') as mock_completion:
+            mock_completion.side_effect = Exception("OllamaException - [Errno 111] Connection refused")
+            
+            llm = LLM(model="ollama/llama3")
+            
+            with pytest.raises(OllamaConnectionException) as exc_info:
+                llm.call([{"role": "user", "content": "Hello"}])
+            
+            assert "Failed to connect to Ollama" in str(exc_info.value)
+            assert "Please make sure Ollama is installed and running" in str(exc_info.value)