Update tox.ini

tox.ini

@@ -9,9 +9,11 @@ setenv =
 ; which get read in from setup.py. If we don't force our locale to a
 ; utf8 one, tox's env is reset. And the install of these 2 packages
 ; fail.
-whitelist_externals = /usr/bin/env
+whitelist_externals = 
+    /usr/bin/env
+    /usr/bin/travis_wait
 ; TEMP, to get cache going on Travis :-/
-install_command = /usr/bin/env LANG=C.UTF-8 travis_wait pip install {opts} {packages}
+install_command = /usr/bin/env LANG=C.UTF-8 /usr/bin/travis_wait pip install {opts} {packages}
 commands =
      py.test --timeout=30 --duration=10 --cov --cov-report= {posargs}
 deps =