this avoids interfering Travis CI's use of virtualenv. Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
force to use virtual env. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>