My problem was that i recently moved my project with virtualenv to another location, due to this activate script had wrong VIRTUAL_ENV path.
$ cat path_to_your_env/bin/activate
... # some declarations
VIRTUAL_ENV="/path_to_your_env/bin/python" # <-- THIS LINE
export VIRTUAL_ENV
... # some declarations
To fix this, just update VIRTUAL_ENV in activate script.
Also you maybe need to fix first line of your bin/pip to link to real python path.