Added an explicit data folder permissions check on startup

It will try resolve the permission issue on its own, but if not successful it will crash with a helpful message.

spoolman/env.py

@@ -2,6 +2,8 @@
 
 import logging
 import os
+import subprocess
+import sys
 from datetime import datetime
 from enum import Enum
 from pathlib import Path
@@ -11,6 +13,8 @@ from urllib import parse
 import pkg_resources
 from platformdirs import user_data_dir
 
+logger = logging.getLogger(__name__)
+
 
 class DatabaseType(Enum):
     """The database type."""
@@ -272,3 +276,53 @@ def get_build_date() -> Optional[datetime]:
     if build_date == "unknown":
         return None
     return datetime.fromisoformat(build_date)
+
+
+def can_write_to_data_dir() -> bool:
+    """Check if the data directory is writable."""
+    try:
+        test_file = get_data_dir().joinpath("test.txt")
+        test_file.touch()
+        test_file.unlink()
+    except:  # noqa: E722
+        return False
+    return True
+
+
+def chown_dir(path: str) -> bool:
+    """Try to chown the data directory to the current user."""
+    if os.name == "nt":
+        return False
+
+    try:
+        uid = os.getuid()
+        gid = os.getgid()
+        subprocess.run(["chown", "-R", f"{uid}:{gid}", path], check=True)  # noqa: S603, S607
+    except:  # noqa: E722
+        return False
+    return True
+
+
+def check_write_permissions() -> None:
+    """Verify that the data directory is writable, crash with a helpful error message if not."""
+    if not can_write_to_data_dir():
+        # If windows we can't fix the permissions, so just crash
+        if os.name == "nt":
+            logger.error("Data directory is not writable.")
+            sys.exit(1)
+
+        # Try fixing it by chowning the directory to the current user
+        logger.warning("Data directory is not writable, trying to fix it...")
+        if not chown_dir(get_data_dir()) or not can_write_to_data_dir():
+            uid = os.getuid()
+            gid = os.getgid()
+
+            logger.error(
+                (
+                    "Data directory is not writable. "
+                    'Please run "sudo chown -R %s:%s /path/to/spoolman/datadir" on the host OS.'
+                ),
+                uid,
+                gid,
+            )
+            sys.exit(1)