USN-6203-2: Django vulnerability

USN-6203-1 fixed a vulnerability in Django. This update provides
the corresponding update for Ubuntu 18.04 ESM.

Original advisory details:

Seokchan Yoon discovered that Django incorrectly handled certain regular
expressions. A remote attacker could possibly use this issue to cause
Django to consume resources, leading to a denial of service.

advisory denial of service django issue regular expressions resources service ubuntu update usn vulnerability yoon