diff --git a/_pytest/mark.py b/_pytest/mark.py
index 06f961496..a619f96ca 100644
--- a/_pytest/mark.py
+++ b/_pytest/mark.py
@@ -2,7 +2,9 @@
 import py
 
 class MarkerError(Exception):
-    """Error in use of a pytest marker/attribute"""
+    """
+    Error in use of a pytest marker/attribute.
+    """
 
 
 def pytest_namespace():