Skip ragas tests if ragas not available

Author: Yun-Kim

riotfile.py

@@ -2885,7 +2885,11 @@ def select_pys(min_version: str = MIN_PYTHON_VERSION, max_version: str = MAX_PYT
             pkgs={"vcrpy": latest, "pytest-asyncio": "==0.21.1"},
             venvs=[
                 Venv(pys="3.7"),
-                Venv(pys=select_pys(min_version="3.8"), pkgs={"ragas": "==0.1.21", "langchain": latest}),
+                Venv(
+                    pys=select_pys(min_version="3.8"),
+                    pkgs={"ragas": "==0.1.21", "langchain": latest},
+                    env={"RAGAS_AVAILABLE": "True"},
+                ),
             ],
         ),
         Venv(