diff --git a/colorlog/escape_codes.py b/colorlog/escape_codes.py
index f35dfca..185b947 100644
--- a/colorlog/escape_codes.py
+++ b/colorlog/escape_codes.py
@@ -5,6 +5,7 @@
 
 Uses colorama as an optional dependency to support color on Windows
 """
+
 import sys
 
 try:
diff --git a/tox.ini b/tox.ini
index db99cc7..a8d1d5f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -7,7 +7,7 @@ commands = pytest -v
 
 [testenv:black]
 deps = black
-commands = black --check colorlog doc
+commands = black --check --diff colorlog doc
 skip_install = true
 
 [testenv:flake8]