tree: fix pylint warnings

This fixes pylint warnings on our modules that are currently not part of
CI-pylint. The fixes should all be straightforward.

Signed-off-by: David Rheinsberg <david.rheinsberg@gmail.com>

devices/org.osbuild.loopback

@@ -18,11 +18,10 @@ documentation for `osbuil.util.udev.UdevInhibitor`.
 
 
 import argparse
-import errno
 import os
 import sys
 
-from typing import Dict, Optional
+from typing import Dict
 
 from osbuild import devices
 from osbuild import loop
@@ -64,6 +63,9 @@ class LoopbackService(devices.DeviceService):
     def __init__(self, args: argparse.Namespace):
         super().__init__(args)
         self.ctl = loop.LoopControl()
+        self.fd = None
+        self.lo = None
+        self.sector_size = None
 
     @staticmethod
     def setup_loop(lo: loop.Loop):

devices/org.osbuild.luks2

@@ -140,11 +140,11 @@ class CryptDeviceService(devices.DeviceService):
         self.devname = None
 
         # finally close the device
-        res = subprocess.run(["cryptsetup", "-q", "close", name],
-                             check=self.check,
-                             stdout=subprocess.PIPE,
-                             stderr=subprocess.STDOUT,
-                             encoding="UTF-8")
+        subprocess.run(["cryptsetup", "-q", "close", name],
+                       check=self.check,
+                       stdout=subprocess.PIPE,
+                       stderr=subprocess.STDOUT,
+                       encoding="UTF-8")
 
 
 def main():

inputs/org.osbuild.ostree

@@ -133,7 +133,7 @@ class OSTreeInput(inputs.InputService):
         if origin == "org.osbuild.pipeline":
             for ref, options in refs.items():
                 source = store.read_tree(ref)
-                with open(os.path.join(source, "compose.json"), "r") as f:
+                with open(os.path.join(source, "compose.json"), "r", encoding="utf8") as f:
                     compose = json.load(f)
                 commit_id = compose["ostree-commit"]
                 reply = export({commit_id: options}, source, target)

inputs/org.osbuild.ostree.checkout

@@ -105,7 +105,7 @@ class OSTreeCheckoutInput(inputs.InputService):
         if origin == "org.osbuild.pipeline":
             for ref, options in refs.items():
                 source = store.read_tree(ref)
-                with open(os.path.join(source, "compose.json"), "r") as f:
+                with open(os.path.join(source, "compose.json"), "r", encoding="utf8") as f:
                     compose = json.load(f)
                 commit_id = compose["ostree-commit"]
                 ids.append(checkout({commit_id: options}, source, target))

mounts/org.osbuild.noop

@@ -34,6 +34,7 @@ SCHEMA_2 = """
 
 
 class NoOpMount(mounts.MountService):
+    mountpoint = None
 
     def mount(self, args: Dict):
         root = args["root"]

mounts/org.osbuild.ostree.deployment

@@ -104,8 +104,6 @@ class OSTreeDeploymentMount(mounts.MountService):
         self.mountpoint = tree
         self.check = True
 
-        return None
-
     def umount(self):
 
         if not self.mountpoint: