hello everyone, i install odoo 11 i follow one of those in the website given. when im trying to start in terminal using this cd opt/odoo/odoo then ./odoo-bin and heres the error 

Traceback (most recent call last):
File "./odoo-bin", line 5, in
import odoo
File "/opt/odoo/odoo/odoo/__init__.py", line 84, in
from . import modules
File "/opt/odoo/odoo/odoo/modules/__init__.py", line 8, in
from . import db, graph, loading, migration, module, registry
File "/opt/odoo/odoo/odoo/modules/graph.py", line 10, in
import odoo.tools as tools
File "/opt/odoo/odoo/odoo/tools/__init__.py", line 8, in
from .config import config
File "/opt/odoo/odoo/odoo/tools/config.py", line 17, in
from passlib.context import CryptContext
ImportError: No module named 'passlib'

can anyone help me regarding this problem