tox: Don't use pip -E

tox.ini

@@ -36,8 +36,8 @@ deps = -r{toxinidir}/requirements/default.txt
        -r{toxinidir}/requirements/py26.txt
        -r{toxinidir}/requirements/test.txt
 commands = {toxinidir}/contrib/release/removepyc.sh {toxinidir}
-           pip -E {envdir} install -r contrib/requirements/py26.txt
-           pip -E {envdir} install -r contrib/requirements/test.txt
+           pip install -r contrib/requirements/py26.txt
+           pip install -r contrib/requirements/test.txt
            nosetests --with-xunit                               \
                      --xunit-file={toxinidir}/nosetests.xml     \
                      --with-coverage3 --cover3-xml              \