This bug was fixed in the package python-apt - 1.6.5ubuntu0.3
--------------- python-apt (1.6.5ubuntu0.3) bionic; urgency=medium
* Don't duplicate disabled sources during add() (LP: #1311056)
-- Dave Jones <email address hidden> Fri, 24 Jan 2020 22:06:25 +0000
This bug was fixed in the package python-apt - 1.6.5ubuntu0.3
---------------
python-apt (1.6.5ubuntu0.3) bionic; urgency=medium
* Don't duplicate disabled sources during add() (LP: #1311056)
-- Dave Jones <email address hidden> Fri, 24 Jan 2020 22:06:25 +0000