From 4969751fde0ef09cd72c738a80c32851c1b1f21d Mon Sep 17 00:00:00 2001
From: Alex Gaynor <alex.gaynor@gmail.com>
Date: Fri, 3 Jan 2014 15:08:45 -0800
Subject: Explanatory comment

---
 setup.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/setup.py b/setup.py
index fe37d9fb..0bdad485 100644
--- a/setup.py
+++ b/setup.py
@@ -33,6 +33,15 @@ requirements = [
 
 
 class cffi_build(build):
+    """
+    This class exists, instead of just providing ``ext_modules=[...]`` directly
+    in ``setup()`` because importing cryptography requires we have several
+    packages installed first.
+
+    By doing the imports here we ensure that packages listed in
+    ``setup_requires`` are already installed.
+    """
+
     def finalize_options(self):
         from cryptography.hazmat.bindings.openssl.binding import Binding
         from cryptography.hazmat.primitives import constant_time, padding
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