py37 (#1256)

* add py37 to travisci

* use dist:xenial for py37

* sudo: true in .travici

* bump websockets version for py37 support and fix unit tests

sanic/server.py

@@ -665,7 +665,7 @@ def serve(host, port, request_handler, error_handler, before_start=None,
         for conn in connections:
             if hasattr(conn, "websocket") and conn.websocket:
                 coros.append(
-                    conn.websocket.close_connection(after_handshake=True)
+                    conn.websocket.close_connection()
                 )
             else:
                 conn.close()

sanic/worker.py

@@ -116,7 +116,7 @@ class GunicornWorker(base.Worker):
             for conn in self.connections:
                 if hasattr(conn, "websocket") and conn.websocket:
                     coros.append(
-                        conn.websocket.close_connection(after_handshake=False)
+                        conn.websocket.close_connection()
                     )
                 else:
                     conn.close()