remove unneeded init in ECB class, add warning to docs for ECB mode
diff --git a/cryptography/primitives/block/modes.py b/cryptography/primitives/block/modes.py
index 0bf8010..ac3392c 100644
--- a/cryptography/primitives/block/modes.py
+++ b/cryptography/primitives/block/modes.py
@@ -24,6 +24,3 @@
 
 class ECB(object):
     name = "ECB"
-
-    def __init__(self):
-        super(ECB, self).__init__()
diff --git a/docs/primitives/symmetric-encryption.rst b/docs/primitives/symmetric-encryption.rst
index 8a9bbbd..d0429d4 100644
--- a/docs/primitives/symmetric-encryption.rst
+++ b/docs/primitives/symmetric-encryption.rst
@@ -72,6 +72,7 @@
 Insecure Modes
 --------------
 
+.. warning:: Do not use. This is an insecure mode.
 .. class:: cryptography.primitives.block.modes.ECB()
 
     ECB (Electronic Code Book) is the simplest mode of operation for block