diff --git a/compare_pages.py b/compare_pages.py
index 4f8e6fe..03f458a 100755
--- a/compare_pages.py
+++ b/compare_pages.py
@@ -159,16 +159,16 @@ def render_teletekst(fname, content):
     # lives, and possibly be wrong there anyway
 
     # Wrap it in the minimally needed HTML
-    content = '''
+    content = f'''
 <html>
   <head>
-    <style>body { background: #202020; }</style>
+    <style>body {{ background: #202020; }}</style>
   </head>
   <body>
     <link href="https://cdn.nos.nl/assets/nos-symfony/ceb1651/bundles/nossite/css/teletekst.css" media="all" type="text/css" rel="stylesheet"/>
-    <pre class="teletekst__content__pre">%s</pre>
+    <pre class="teletekst__content__pre">{content}</pre>
   </body>
-</html>''' % (content,)
+</html>'''
     imgkit.from_string(
         content,
         fname,
diff --git a/walk_pages.py b/walk_pages.py
index 02aee2c..66e8051 100755
--- a/walk_pages.py
+++ b/walk_pages.py
@@ -50,7 +50,10 @@ def handle_data(self, data):
         self.text_collected += data
 
     def error(self, message):
-        print(f"Parsing error: {message}")
+        """
+        Implement abstract error() function
+        """
+        print(f"[{self}] Parsing error: {message}")
 
 
 def parse_headlines(text):
@@ -100,8 +103,8 @@ def fetch_page(page, http, stamp, is_index):
 
     try:
         page_json = json.loads(result.data)
-    except ValueError as e:
-        print(f"Error parsing JSON: {e}")
+    except ValueError as err:
+        print(f"Error parsing JSON: {err}")
         print(result.data)
         sys.exit(1)
 
