We should consider *actually* testing Twisted. (#579)

diff --git a/tox.ini b/tox.ini
index f323bb0..bc4a04f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -29,7 +29,7 @@
 commands =
     python -c "import OpenSSL.SSL; print(OpenSSL.SSL.SSLeay_version(OpenSSL.SSL.SSLEAY_VERSION))"
     python -c "import cryptography; print(cryptography.__version__)"
-    python -m twisted.trial
+    python -m twisted.trial --reporter=text twisted
 
 [testenv:py35-urllib3Master]
 basepython=python3.5