anchor.diff:  
   with python3.pkgs;
   
  -buildPythonPackage rec {
  +let
  +  # officially supported database drivers
  +  dbDrivers = [
  +    psycopg2
  +    # sqlite driver is already shipped with python by default
  +  ];
  +
  +in buildPythonPackage rec {
     pname = "mautrix-telegram";
     version = "0.8.2";
     disabled = pythonOlder "3.6";
  
positive.code:   # Hence we need to patch away `alembic` from `mautrix-telegram` and create an `alembic`
    # which has `mautrix-telegram` in its environment.
    passthru.alembic = alembic.overrideAttrs (old: {
      propagatedBuildInputs = old.propagatedBuildInputs ++ [
        mautrix-telegram
      ];
    });
  
negative.code:     pillow
      lxml
      setuptools
    ] ++ dbDrivers;
  
    # `alembic` (a database migration tool) is only needed for the initial setup,
    # and not needed during the actual runtime. However `alembic` requires `mautrix-telegram`
  