Python 2.6 support would be dropped by
Infra team from mitaka,CI would no longer be testing it,
so projects should drop it too.
Change-Id: I20288880b29061920a54c6c1cc8618b67e70526a
When a development environment is under a proxy, tox is failed even if
environment variables of the proxy are set.
This patch fixes this problem.
Closes-Bug: #1525115
Change-Id: Iff6d29445cbb88c041c58e87720300ef8ec38265