Fix tox deps inheritance

Author: etingof

tox.ini

@@ -17,6 +17,7 @@ install_command =
 [testenv:unittest]
 deps =
     discover
+    {[testenv]deps}
     -r{toxinidir}/test-requirements.txt
     -r{toxinidir}/requirements.txt
 commands =
@@ -71,6 +72,7 @@ setenv =
    {[testenv]setenv}
    PYTHON=coverage run --parallel-mode
 deps =
+    {[testenv:unittest]deps}
     coverage
     discover
 commands = coverage erase