SSL issue while building cyphon and installing django-auth-ldap

Hi im using latest docker version on Ubuntu 18.
so basically im trying to install django ldap auth module for cyphon via Docker file and building the image. But everytime i build image adding django-auth-ldap to dockerfile i end-up with errors :-

ERROR: unsatisfiable constraints:
** build-deps-0:**
** masked in: cache**
** satisfies: world[build-deps]**
** django-auth-ldap (missing):**
** required by:**

pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.

Docker file:-