diff --git a/scripts/imgtool/keys/ecdsa.py b/scripts/imgtool/keys/ecdsa.py
index 0433beb..79e4bb8 100644
--- a/scripts/imgtool/keys/ecdsa.py
+++ b/scripts/imgtool/keys/ecdsa.py
@@ -12,9 +12,11 @@
 
 from .general import KeyClass
 
+
 class ECDSAUsageError(Exception):
     pass
 
+
 class ECDSA256P1Public(KeyClass):
     def __init__(self, key):
         self.key = key
@@ -160,7 +162,8 @@
         return priv
 
     def export_private(self, path, passwd=None):
-        """Write the private key to the given file, protecting it with the optional password."""
+        """Write the private key to the given file, protecting it with '
+          'the optional password."""
         if passwd is None:
             enc = serialization.NoEncryption()
         else: