gnu: Add python-tornado.

* gnu/packages/python.scm (python-tornado, python2-tornado): New variables.

gnu/packages/python.scm

@@ -3536,6 +3536,41 @@ (define-public python-singledispatch
 (define-public python2-singledispatch
   (package-with-python2 python-singledispatch))
 
+(define-public python-tornado
+  (package
+    (name "python-tornado")
+    (version "4.1")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (string-append
+             "https://pypi.python.org/packages/source/t/tornado/"
+             "tornado-" version ".tar.gz"))
+       (sha256
+        (base32 "0a12f00h277zbifibnj46wf14801f573irvf6hwkgja5vspd7awr"))))
+    (build-system python-build-system)
+    (inputs
+     `(("python-certifi" ,python-certifi)))
+    (native-inputs
+     `(("python-setuptools" ,python-setuptools)))
+    (home-page "https://pypi.python.org/pypi/tornado/4.1")
+    (synopsis "Python web framework and asynchronous networking library")
+    (description
+     "Tornado is a Python web framework and asynchronous networking library,
+originally developed at FriendFeed.  By using non-blocking network I/O,
+Tornado can scale to tens of thousands of open connections, making it ideal
+for long polling, WebSockets, and other applications that require a long-lived
+connection to each user.")
+    (license asl2.0)))
+
+(define-public python2-tornado
+  (let ((tornado (package-with-python2 python-tornado)))
+    (package (inherit tornado)
+      (inputs
+       `(("python2-backport-ssl-match-hostname"
+          ,python2-backport-ssl-match-hostname)
+         ,@(package-inputs tornado))))))
+
 (define-public python-waf
   (package
     (name "python-waf")