minor improvements

main.py

@@ -139,7 +139,7 @@ def sign_invoice(id):
         ),
         "-b", "LOCAL",  # use local Bürgerkarte
         "-a",  # automatically position signature
-        "-v", "true" if name == "Rechnung" else "false",
+        "-v", "true" if name == "Rechnung" else "false",  # set visibility
         "-s"  # save without asking
     ]
     print(" ".join(command))

utils.py

@@ -11,7 +11,7 @@ readline  # this does nothing but make sure the import readline is not removed a
 
 def load_yaml(filename):
     with open(filename, 'r') as stream:
-        return yaml.load(stream)
+        return yaml.safe_load(stream)
 
 
 def save_yaml(data, filename):