wip: refactor get_drives

foris_controller_backends/storage/__init__.py

 import logging
 import os
+import pathlib
 import shlex
 
 from foris_controller_backends.uci import UciBackend, get_option_named, parse_bool, store_bool
@@ -118,6 +119,9 @@ class SettingsUci(BaseCmdLine, BaseFile):
 
 
 class DriveManager(BaseCmdLine, BaseFile):
+    FORMATING_FILE = "/tmp/storage_plugin/formating"
+    DRIVES_DIR = "/sys/class/block"
+
     def _find_blkid_bin(self) -> str:
         """ finds fullpath to blkid binary """
         for dirpath in [e for e in os.environ.get("PATH", "").split(":") if e.startswith("/")] + [
@@ -129,30 +133,27 @@ class DriveManager(BaseCmdLine, BaseFile):
 
         return "/usr/sbin/blkid"  # default path
 
+    def _is_mount_root(self, device: str) -> bool:
+        """ Check whether device is mounted as rootfs ('/') """
+        mount = ""
+        try:
+            mount = self._read_and_parse(
+                "/proc/mounts", r"^/dev/{} (/[^ ]*) .*".format(device)
+            )
+        except FailedToParseFileContent:
+            return False
+
+        return mount == "/"
+
     def get_drives(self):
         ret = []
         # Would block during formating
-        if os.path.isfile(inject_file_root("/tmp/storage_plugin/formating")):
+        if pathlib.Path(inject_file_root(self.FORMATING_FILE)).is_file():
             return {"drives": ret}
 
-        drive_dir = "/sys/class/block"
-
-        for dev in os.listdir(inject_file_root(drive_dir)):
-            # skip some device
-            if not dev.startswith("sd"):
-                continue
-
-            # is device mounted somewhere
-            mount = ""
-            try:
-                mount = self._read_and_parse(
-                    "/proc/mounts", r"^/dev/{} (/[^ ]*) .*".format(dev)
-                )
-            except FailedToParseFileContent:
-                pass
-
-            # skip devices mounted as root
-            if mount == "/":
+        for dev in pathlib.Path(inject_file_root(self.DRIVES_DIR)).glob("sd*"):
+            # skip device mounted as root
+            if self._is_mount_root(dev.name):
                 continue
 
             retval, stdout, _ = self._run_command(self._find_blkid_bin(), "/dev/%s" % dev)