diff --git a/stacosys/db/dao.py b/stacosys/db/dao.py
index 7d9abdb..5a91210 100644
--- a/stacosys/db/dao.py
+++ b/stacosys/db/dao.py
@@ -28,29 +28,29 @@ def delete_comment(comment: Comment):
 
 
 def find_not_notified_comments():
-    return db()(db().comment.notified == None).select()
+    return db()(db().comment.notified is None).select()
 
 
 def find_not_published_comments():
-    return db()(db().comment.published == None).select()
+    return db()(db().comment.published is None).select()
 
 
 def find_published_comments_by_url(url):
-    return db()((db().comment.url == url) & (db().comment.published != None)).select(
+    return db()((db().comment.url == url) & (db().comment.published is not None)).select(
         orderby=db().comment.published
     )
 
 
 def count_published_comments(url):
     return (
-        db()((db().comment.url == url) & (db().comment.published != None)).count()
+        db()((db().comment.url == url) & (db().comment.published is not None)).count()
         if url
-        else db()(db().comment.published != None).count()
+        else db()(db().comment.published is not None).count()
     )
 
 
 def find_recent_published_comments():
-    return db()(db().comment.published != None).select(
+    return db()(db().comment.published is not None).select(
         orderby=~db().comment.published, limitby=(0, 10)
     )
 
diff --git a/stacosys/service/configuration.py b/stacosys/service/configuration.py
index 986409e..67129a4 100644
--- a/stacosys/service/configuration.py
+++ b/stacosys/service/configuration.py
@@ -36,12 +36,13 @@ class Config:
     def load(self, config_pathname):
         self._cfg.read(config_pathname)
 
-    def _split_key(self, key: ConfigParameter):
+    @staticmethod
+    def _split_key(key: ConfigParameter):
         section, param = str(key.value).split(".")
         if not param:
             param = section
             section = ""
-        return (section, param)
+        return section, param
 
     def exists(self, key: ConfigParameter):
         section, param = self._split_key(key)
@@ -78,8 +79,8 @@ class Config:
     def check(self):
         for key in ConfigParameter:
             if not self.get(key):
-                return (False, key.value)
-        return (True, None)
+                return False, key.value
+        return True, None
 
     def __repr__(self):
         dict_repr = {}
diff --git a/stacosys/service/mail.py b/stacosys/service/mail.py
index d7fe5ca..8589e60 100644
--- a/stacosys/service/mail.py
+++ b/stacosys/service/mail.py
@@ -18,11 +18,11 @@ class Mailer:
         self._site_admin_email: str = ""
 
     def configure_smtp(
-        self,
-        smtp_host,
-        smtp_port,
-        smtp_login,
-        smtp_password,
+            self,
+            smtp_host,
+            smtp_port,
+            smtp_login,
+            smtp_password,
     ) -> None:
         self._smtp_host = smtp_host
         self._smtp_port = smtp_port