Add enviroment validation at server startup phase (#3388)

### What problem does this PR solve?

1. Validate the Python version should >= 3.11
2. Download nltk data

### Type of change

- [x] New Feature (non-breaking change which adds functionality)
- [x] Refactoring

---------

Signed-off-by: jinhai <haijin.chn@gmail.com>
Co-authored-by: jinhai <haijin.chn@gmail.com>
Co-authored-by: Zhichang Yu <yuzhichang@gmail.com>

api/ragflow_server.py

@@ -22,6 +22,7 @@ import time
 import traceback
 from concurrent.futures import ThreadPoolExecutor
 
+import validation
 from werkzeug.serving import run_simple
 from api.apps import app
 from api.db.runtime_config import RuntimeConfig

api/validation.py

@@ -0,0 +1,37 @@
+#
+#  Copyright 2024 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+import sys
+from api.utils.log_utils import logger
+
+def python_version_validation():
+    # Check python version
+    required_python_version = (3, 10)
+    if sys.version_info < required_python_version:
+        logger.info(
+            f"Required Python: >= {required_python_version[0]}.{required_python_version[1]}. Current Python version: {sys.version_info[0]}.{sys.version_info[1]}."
+        )
+        sys.exit(1)
+    else:
+        logger.info(f"Python version: {sys.version_info[0]}.{sys.version_info[1]}")
+
+
+python_version_validation()
+
+# Download nltk data
+import nltk
+nltk.download('wordnet')
+nltk.download('punkt_tab')