Fix tox.ini to support Travis' old pypy

Gasper Zejn · Gasper Zejn · commit 6d6a49927032 · 2017-04-14T11:46:17.000+02:00
diff --git a/tox.ini b/tox.ini
@@ -12,3 +12,5 @@ deps =
     pytest
     pytest-cov
     pytest-runner
+    ; Because Travis' pypy only works with old Cryptography
+    pypy: cryptography == 0.9
