diff --git a/buildbot_nix/models.py b/buildbot_nix/models.py
index 6198506..2acdcd9 100644
--- a/buildbot_nix/models.py
+++ b/buildbot_nix/models.py
@@ -1,23 +1,26 @@
 from enum import Enum
 from pathlib import Path
 
-from pydantic import BaseModel, Field, field_serializer, field_validator, ConfigDict
-from buildbot.plugins import util, steps
+from buildbot.plugins import steps, util
+from pydantic import BaseModel, ConfigDict, Field
 
 from .secrets import read_secret_file
 
-class InternalIssue(Exception):
+
+class InternalError(Exception):
     pass
 
 
 def exclude_fields(fields: list[str]) -> dict[str, dict[str, bool]]:
-    return dict(map(lambda k: (k, {"exclude": True}), fields))
+    return {k: {"exclude": True} for k in fields}
+
 
 class AuthBackendConfig(str, Enum):
     github = "github"
     gitea = "gitea"
     none = "none"
 
+
 class CachixConfig(BaseModel):
     name: str
 
@@ -27,13 +30,13 @@ class CachixConfig(BaseModel):
     @property
     def signing_key(self) -> str:
         if self.signing_key_file is None:
-            raise InternalIssue
+            raise InternalError
         return read_secret_file(self.signing_key_file)
 
     @property
     def auth_token(self) -> str:
         if self.auth_token_file is None:
-            raise InternalIssue
+            raise InternalError
         return read_secret_file(self.auth_token_file)
 
     # TODO why did the original implementation return an empty env if both files were missing?
@@ -47,13 +50,14 @@ class CachixConfig(BaseModel):
     class Config:
         fields = exclude_fields(["singing_key", "auth_token"])
 
+
 class GiteaConfig(BaseModel):
     instance_url: str
     topic: str | None
 
-    token_file: Path = Field(default = Path("gitea-token"))
-    webhook_secret_file: Path = Field(default = Path("gitea-webhook-secret"))
-    project_cache_file: Path = Field(default = Path("gitea-project-cache.json"))
+    token_file: Path = Field(default=Path("gitea-token"))
+    webhook_secret_file: Path = Field(default=Path("gitea-webhook-secret"))
+    project_cache_file: Path = Field(default=Path("gitea-project-cache.json"))
 
     oauth_id: str | None
     oauth_secret_file: Path | None
@@ -69,12 +73,13 @@ class GiteaConfig(BaseModel):
     @property
     def oauth_secret(self) -> str:
         if self.oauth_secret_file is None:
-            raise InternalIssue
+            raise InternalError
         return read_secret_file(self.oauth_secret_file)
 
     class Config:
         fields = exclude_fields(["token", "webhook_secret", "oauth_secret"])
 
+
 class GitHubLegacyConfig(BaseModel):
     token_file: Path
 
@@ -85,19 +90,18 @@ class GitHubLegacyConfig(BaseModel):
     class Config:
         fields = exclude_fields(["token"])
 
+
 class GitHubAppConfig(BaseModel):
     id: int
 
     secret_key_file: Path
-    installation_token_map_file: Path = Field(default = Path(
-        "github-app-installation-token-map.json"
-    ))
-    project_id_map_file: Path = Field(default = Path(
-        "github-app-project-id-map-name.json"
-    ))
-    jwt_token_map: Path = Field(default = Path(
-        "github-app-jwt-token"
-    ))
+    installation_token_map_file: Path = Field(
+        default=Path("github-app-installation-token-map.json")
+    )
+    project_id_map_file: Path = Field(
+        default=Path("github-app-project-id-map-name.json")
+    )
+    jwt_token_map: Path = Field(default=Path("github-app-jwt-token"))
 
     @property
     def secret_key(self) -> str:
@@ -106,12 +110,13 @@ class GitHubAppConfig(BaseModel):
     class Config:
         fields = exclude_fields(["secret_key"])
 
+
 class GitHubConfig(BaseModel):
     auth_type: GitHubLegacyConfig | GitHubAppConfig
     topic: str | None
 
-    project_cache_file: Path = Field(default = Path("github-project-cache-v1.json"))
-    webhook_secret_file: Path = Field(default = Path("github-webhook-secret"))
+    project_cache_file: Path = Field(default=Path("github-project-cache-v1.json"))
+    webhook_secret_file: Path = Field(default=Path("github-webhook-secret"))
 
     oauth_id: str | None
     oauth_secret_file: Path | None
@@ -123,16 +128,17 @@ class GitHubConfig(BaseModel):
     @property
     def oauth_secret(self) -> str:
         if self.oauth_secret_file is None:
-            raise InternalIssue
+            raise InternalError
         return read_secret_file(self.oauth_secret_file)
 
+
 # note that serialization isn't correct, as there is no way to *rename* the field `nix_type` to `_type`,
 # one must always specify `by_alias = True`, such as `model_dump(by_alias = True)`, relevant issue:
 # https://github.com/pydantic/pydantic/issues/8379
 class Interpolate(BaseModel):
     model_config = ConfigDict(populate_by_name=True)
 
-    nix_type: str = Field(alias = "_type")
+    nix_type: str = Field(alias="_type")
     value: str
 
 
@@ -148,15 +154,12 @@ class PostBuildStep(BaseModel):
             return util.Interpolate(value.value)
 
         return steps.ShellCommand(
-            name = self.name,
-            env = {
-                k: maybe_interpolate(k) for k in self.environment
-            },
-            command = [
-                maybe_interpolate(x) for x in self.command
-            ]
+            name=self.name,
+            env={k: maybe_interpolate(k) for k in self.environment},
+            command=[maybe_interpolate(x) for x in self.command],
         )
 
+
 class BuildbotNixConfig(BaseModel):
     db_url: str
     auth_backend: AuthBackendConfig
@@ -169,7 +172,7 @@ class BuildbotNixConfig(BaseModel):
     build_systems: list[str]
     eval_max_memory_size: int
     eval_worker_count: int | None
-    nix_workers_secret_file: Path = Field(default = Path("buildbot-nix-workers"))
+    nix_workers_secret_file: Path = Field(default=Path("buildbot-nix-workers"))
     domain: str
     webhook_base_url: str
     use_https: bool