Upgrade 2.1.9 to 3.0.0rc1 - can not drop function st_union(geometry) because other objects depend on it

[robe]

I'm not sure this test is fair — dronie is showing this error going from 2.1.9 to 3.0.0rc1

​https://dronie.osgeo.org/postgis/postgis/669

Died at ../run_test.pl line 1588.
failed (Error encountered altering EXTENSION POSTGIS: /tmp/pgis_reg/regress_log)
-----------------------------------------------------------------------------
CREATE EXTENSION
WARNING: unpackaging raster
WARNING: PostGIS Raster functionality has been unpackaged
HINT: type `SELECT postgis_extensions_upgrade(); to finish the upgrade. After upgrading, if you want to drop raster, run: DROP EXTENSION postgis_raster;
ERROR: cannot drop function st_union(geometry) because other objects depend on it
DETAIL: view upgrade_view_test depends on function st_union(geometry)
HINT: Use DROP ... CASCADE to drop the dependent objects too.
CONTEXT: SQL statement "DROP AGGREGATE IF EXISTS ST_Union (geometry)"
PL/pgSQL function inline_code_block line 15 at EXECUTE
-----------------------------------------------------------------------------
make[1]: *** [check] Error 1
make[1]: Leaving directory `/drone/src/regress/core'
make: *** [check-regress] Error 2
make: Leaving directory `/drone/src/regress'
FAIL: upgrade 2.1.9--3.0.0rc1 

Can we not test 2.1.9 as that's long deprecated already and besides we know that ST_Union changed. It's changed I think 3 times since 2.1.9 so this is an expected failure