Unit tests covering missing username or password
Unit tests covering missing username or password

After fixing message displayed when client is executed without
required environment variables exported (OS_USERNAME, OS_PASSWORD,
OS_PROJECT_NAME, OS_AUTH_URL) regression tests should be added. I've
also fixed an issue causing tests using make_env method to always use
FAKE_V2_ENV, even in ShellTestWithKeystoneV3Auth.

Change-Id: I800c8fa11ee45d19f179bd030426db86a93d9f6a
Closes-Bug: 1419788
Partial-Bug: 1355252

varunarya10/python-glanceclient,openstack/python-glanceclient,JioCloud/python-glanceclient,JioCloud/python-glanceclient,klmitch/python-glanceclient,mmasaki/python-glanceclient,mmasaki/python-glanceclient,klmitch/python-glanceclient,varunarya10/python-glanceclient,openstack/python-glanceclient