select txaio subsystem in 'base' tests

autobahn/wamp/test/test_protocol_peer.py

@@ -25,6 +25,16 @@
 ###############################################################################
 
 from __future__ import absolute_import
+import os
+
+# we need to select a txaio subsystem because we're importing the base
+# protocol classes here for testing purposes. "normally" you'd import
+# from autobahn.twisted.wamp or autobahn.asyncio.wamp explicitly.
+import txaio
+if os.environ.get('USE_TWISTED', False):
+    txaio.use_twisted()
+else:
+    txaio.use_asyncio()
 
 from autobahn import wamp
 from autobahn.wamp import message