diff --git a/nixpkgs_review/builddir.py b/nixpkgs_review/builddir.py
index af055e4..2ccfc79 100644
--- a/nixpkgs_review/builddir.py
+++ b/nixpkgs_review/builddir.py
@@ -30,8 +30,8 @@ def create_cache_directory(name: str) -> Union[Path, "TemporaryDirectory[str]"]:
         if home is None:
             # we are in a temporary directory
             return TemporaryDirectory()
-        else:
-            xdg_cache = Path(home).joinpath(".cache")
+
+        xdg_cache = Path(home).joinpath(".cache")
 
     counter = 0
     while True:
diff --git a/nixpkgs_review/cli/__init__.py b/nixpkgs_review/cli/__init__.py
index 4316403..69a1663 100644
--- a/nixpkgs_review/cli/__init__.py
+++ b/nixpkgs_review/cli/__init__.py
@@ -120,13 +120,13 @@ def hub_config_path() -> Path:
     raw_hub_path = os.environ.get("HUB_CONFIG", None)
     if raw_hub_path:
         return Path(raw_hub_path)
+
+    raw_config_home = os.environ.get("XDG_CONFIG_HOME", None)
+    if raw_config_home is None:
+        config_home = Path.home().joinpath(".config")
     else:
-        raw_config_home = os.environ.get("XDG_CONFIG_HOME", None)
-        if raw_config_home is None:
-            config_home = Path.home().joinpath(".config")
-        else:
-            config_home = Path(raw_config_home)
-        return config_home.joinpath("hub")
+        config_home = Path(raw_config_home)
+    return config_home.joinpath("hub")
 
 
 def read_github_token() -> str | None:
@@ -313,7 +313,7 @@ def parse_args(command: str, args: list[str]) -> argparse.Namespace:
 
     if args == []:
         main_parser.print_help()
-        exit(2)
+        sys.exit(2)
 
     return main_parser.parse_args(args)
 
diff --git a/nixpkgs_review/errors.py b/nixpkgs_review/errors.py
index 743d88f..8549cf9 100644
--- a/nixpkgs_review/errors.py
+++ b/nixpkgs_review/errors.py
@@ -1,4 +1,2 @@
 class NixpkgsReviewError(Exception):
     """Base class for exceptions in this module."""
-
-    pass
diff --git a/nixpkgs_review/github.py b/nixpkgs_review/github.py
index 56a704e..6e18911 100644
--- a/nixpkgs_review/github.py
+++ b/nixpkgs_review/github.py
@@ -26,8 +26,8 @@ def _request(
             body = json.dumps(data).encode("ascii")
 
         req = urllib.request.Request(url, headers=headers, method=method, data=body)
-        resp = urllib.request.urlopen(req)
-        return json.loads(resp.read())
+        with urllib.request.urlopen(req) as resp:
+            return json.loads(resp.read())
 
     def get(self, path: str) -> Any:
         return self._request(path, "GET")
@@ -42,7 +42,7 @@ def comment_issue(self, pr: int, msg: str) -> Any:
         "Post a comment on a PR with nixpkgs-review report"
         print(f"Posting result comment on {pr_url(pr)}")
         return self.post(
-            f"/repos/NixOS/nixpkgs/issues/{pr}/comments", data=dict(body=msg)
+            f"/repos/NixOS/nixpkgs/issues/{pr}/comments", data={"body": msg}
         )
 
     def approve_pr(self, pr: int) -> Any:
@@ -50,7 +50,7 @@ def approve_pr(self, pr: int) -> Any:
         print(f"Approving {pr_url(pr)}")
         return self.post(
             f"/repos/NixOS/nixpkgs/pulls/{pr}/reviews",
-            data=dict(event="APPROVE"),
+            data={"event": "APPROVE"},
         )
 
     def merge_pr(self, pr: int) -> Any:
@@ -59,7 +59,7 @@ def merge_pr(self, pr: int) -> Any:
         return self.put(f"/repos/NixOS/nixpkgs/pulls/{pr}/merge")
 
     def graphql(self, query: str) -> dict[str, Any]:
-        resp = self.post("/graphql", data=dict(query=query))
+        resp = self.post("/graphql", data={"query": query})
         if "errors" in resp:
             raise RuntimeError(f"Expected data from graphql api, got: {resp}")
         data: dict[str, Any] = resp["data"]
@@ -88,10 +88,13 @@ def get_borg_eval_gist(self, pr: dict[str, Any]) -> dict[str, set[str]] | None:
                 raw_gist_url = (
                     f"https://gist.githubusercontent.com/GrahamcOfBorg/{gist_hash}/raw/"
                 )
-                for line in urllib.request.urlopen(raw_gist_url):
-                    if line == b"":
-                        break
-                    system, attribute = line.decode("utf-8").split()
-                    packages_per_system[system].add(attribute)
+
+                with urllib.request.urlopen(raw_gist_url) as resp:
+                    for line in resp:
+                        if line == b"":
+                            break
+                        system, attribute = line.decode("utf-8").split()
+                        packages_per_system[system].add(attribute)
+
                 return packages_per_system
         return None
diff --git a/nixpkgs_review/review.py b/nixpkgs_review/review.py
index 278b1ab..84e72f2 100644
--- a/nixpkgs_review/review.py
+++ b/nixpkgs_review/review.py
@@ -3,12 +3,12 @@
 import subprocess
 import sys
 import tempfile
-import xml.etree.ElementTree as ElementTree
 from dataclasses import dataclass, field
 from enum import Enum
 from pathlib import Path
 from re import Pattern
 from typing import IO
+from xml.etree import ElementTree
 
 from .allow import AllowedFeatures
 from .builddir import Builddir
@@ -135,9 +135,9 @@ def git_merge(self, commit: str) -> None:
     def apply_unstaged(self, staged: bool = False) -> None:
         args = ["git", "--no-pager", "diff", "--no-ext-diff"]
         args.extend(["--staged"] if staged else [])
-        diff_proc = subprocess.Popen(args, stdout=subprocess.PIPE)
-        assert diff_proc.stdout
-        diff = diff_proc.stdout.read()
+        with subprocess.Popen(args, stdout=subprocess.PIPE) as diff_proc:
+            assert diff_proc.stdout
+            diff = diff_proc.stdout.read()
 
         if not diff:
             info("No diff detected, stopping review...")
diff --git a/nixpkgs_review/utils.py b/nixpkgs_review/utils.py
index 0f98a7b..3245f4c 100644
--- a/nixpkgs_review/utils.py
+++ b/nixpkgs_review/utils.py
@@ -70,5 +70,5 @@ def nix_nom_tool() -> str:
     "Return `nom` if found in $PATH"
     if shutil.which("nom"):
         return "nom"
-    else:
-        return "nix"
+
+    return "nix"