Pass all DOCKER_ env vars to py.test

This ensures that `tox` will run against SSL-protected Docker daemons.

Signed-off-by: Aanand Prasad <[email protected]>

tox.ini

@@ -6,6 +6,8 @@ usedevelop=True
 passenv =
     LD_LIBRARY_PATH
     DOCKER_HOST
+    DOCKER_CERT_PATH
+    DOCKER_TLS_VERIFY
 setenv =
     HOME=/tmp
 deps =