More informative error message if no protocol found for http2

hyper/http20/connection.py

@@ -375,7 +375,10 @@ def connect(self):
                 proto = H2C_PROTOCOL
 
             log.debug("Selected NPN protocol: %s", proto)
-            assert proto in H2_NPN_PROTOCOLS or proto == H2C_PROTOCOL
+            assert proto in H2_NPN_PROTOCOLS or proto == H2C_PROTOCOL, (
+                "No suitable protocol found. Supported protocols: %s. "
+                "Check your OpenSSL version."
+            ) % ','.join(H2_NPN_PROTOCOLS + [H2C_PROTOCOL])
 
             self._sock = BufferedSocket(sock, self.network_buffer_size)
 

test/test_http20.py

@@ -0,0 +1,42 @@
+# -*- coding: utf-8 -*-
+"""
+test_http20.py
+~~~~~~~~~~~~~~
+
+Unit tests for hyper's HTTP/2.0 implementation.
+"""
+import pytest
+from mock import patch
+
+from server import SocketLevelTest
+
+
+class TestHTTP20Connection(SocketLevelTest):
+    h2 = True
+
+    def test_useful_error_with_no_protocol(self):
+        self.set_up()
+
+        def socket_handler(listener):
+            sock = listener.accept()[0]
+            sock.close()
+
+        self._start_server(socket_handler)
+        conn = self.get_connection()
+
+        with patch('hyper.http20.connection.wrap_socket') as mock:
+            mock.return_value = (None, None)
+            with pytest.raises(AssertionError) as exc_info:
+                conn.connect()
+        assert (
+            "No suitable protocol found."
+            in
+            str(exc_info)
+        )
+        assert (
+            "Check your OpenSSL version."
+            in
+            str(exc_info)
+        )
+
+        self.tear_down()

test/test_integration.py

@@ -12,6 +12,7 @@
 import hyper
 import hyper.http11.connection
 import pytest
+from mock import patch
 from h2.frame_buffer import FrameBuffer
 from hyper.compat import ssl
 from hyper.contrib import HTTP20Adapter
@@ -34,8 +35,8 @@
     hyper.tls._context.check_hostname = False
     hyper.tls._context.verify_mode = ssl.CERT_NONE
 
-    # Cover our bases because NPN doesn't yet work on all our test platforms.
-    hyper.http20.connection.H2_NPN_PROTOCOLS += ['', None]
+# Cover our bases because NPN doesn't yet work on all our test platforms.
+PROTOCOLS = hyper.http20.connection.H2_NPN_PROTOCOLS + ['', None]
 
 
 def decode_frame(frame_data):
@@ -76,6 +77,7 @@ def receive_preamble(sock):
     return
 
 
+@patch('hyper.http20.connection.H2_NPN_PROTOCOLS', PROTOCOLS)
 class TestHyperIntegration(SocketLevelTest):
     # These are HTTP/2 tests.
     h2 = True
@@ -1031,6 +1033,7 @@ def socket_handler(listener):
         self.tear_down()
 
 
+@patch('hyper.http20.connection.H2_NPN_PROTOCOLS', PROTOCOLS)
 class TestRequestsAdapter(SocketLevelTest):
     # This uses HTTP/2.
     h2 = True