Check minimum python version before launching (#5795)

* Check minimum python version before launching

* Add link to docs

InvenTree/InvenTree/settings.py

@@ -26,10 +26,12 @@ from dotenv import load_dotenv
 
 from InvenTree.config import get_boolean_setting, get_custom_file, get_setting
 from InvenTree.sentry import default_sentry_dsn, init_sentry
-from InvenTree.version import inventreeApiVersion
+from InvenTree.version import checkMinPythonVersion, inventreeApiVersion
 
 from . import config
 
+checkMinPythonVersion()
+
 INVENTREE_NEWS_URL = 'https://inventree.org/news/feed.atom'
 
 # Determine if we are running in "test" mode e.g. "manage.py test"

InvenTree/InvenTree/version.py

@@ -7,6 +7,7 @@ import os
 import pathlib
 import platform
 import re
+import sys
 from datetime import datetime as dt
 from datetime import timedelta as td
 
@@ -28,6 +29,27 @@ except (NotGitRepository, FileNotFoundError):
     main_commit = None
 
 
+def checkMinPythonVersion():
+    """Check that the Python version is at least 3.9"""
+
+    version = sys.version.split(" ")[0]
+    docs = "https://docs.inventree.org/en/stable/start/intro/#python-requirements"
+
+    msg = f"""
+    InvenTree requires Python 3.9 or above - you are running version {version}.
+    - Refer to the InvenTree documentation for more information:
+    - {docs}
+    """
+
+    if sys.version_info.major < 3:
+        raise RuntimeError(msg)
+
+    if sys.version_info.major == 3 and sys.version_info.minor < 9:
+        raise RuntimeError(msg)
+
+    print(f"Python version {version} - {sys.executable}")
+
+
 def inventreeInstanceName():
     """Returns the InstanceName settings for the current database."""
     import common.models