Add method for checking OS version.

src/openflexure_microscope_server/things/system.py

@@ -5,6 +5,7 @@ the microscope, server, and thing states to the web API.
 """
 
 import os
+import re
 import socket
 import subprocess
 import time
@@ -22,6 +23,8 @@ from openflexure_microscope_server.utilities import VersionData, robust_version_
 SHUTDOWN_CMD = ["sudo", "shutdown", "-h", "now"]
 REBOOT_CMD = ["sudo", "shutdown", "-r", "now"]
 
+OS_VERSION_FILE = "/usr/lib/os-release"
+
 
 class CommandOutput(BaseModel):
     """A pydantic model passing the STDOUT and STDERR from a subprocess over HTTP."""
@@ -81,6 +84,24 @@ class OpenFlexureSystem(lt.Thing):
         """Return True if running on a Raspberry Pi."""
         return os.path.exists("/usr/bin/raspi-config")
 
+    @lt.property
+    def os_version(self) -> Optional[str]:
+        """Return the OS version of the Pi. Returns None if not on a Pi."""
+        if not self.is_raspberrypi:
+            return None
+
+        if not os.path.isfile(OS_VERSION_FILE):
+            return "unknown"
+
+        with open(OS_VERSION_FILE, "r", encoding="utf-8") as os_file:
+            os_data = os_file.read()
+
+        version_match = re.search(r"^VERSION_CODENAME=(.+)$", os_data, re.MULTILINE)
+        if not version_match:
+            return "unknown"
+
+        return version_match.group(1)
+
     @lt.action
     def shutdown(self) -> CommandOutput:
         """Attempt to shutdown the device."""