update CKAN version for unit tests

[andrewphilipsmith]

No description provided.

[frafra]

It would be nice to have the CI tests work again. It looks like there is a problem with the PostgreSQL version:

  Downloading https://files.pythonhosted.org/packages/36/77/894a5dd9f3f55cfc85682d3e6473ee5103d8d418b95baf4019fad3ffa026/psycopg2-2.4.5.tar.gz (719kB)
    100% |████████████████████████████████| 727kB 1.9MB/s 
    Complete output from command python setup.py egg_info:
    running egg_info
    creating pip-egg-info/psycopg2.egg-info
    writing pip-egg-info/psycopg2.egg-info/PKG-INFO
    writing top-level names to pip-egg-info/psycopg2.egg-info/top_level.txt
    writing dependency_links to pip-egg-info/psycopg2.egg-info/dependency_links.txt
    writing manifest file 'pip-egg-info/psycopg2.egg-info/SOURCES.txt'
    Error: could not determine PostgreSQL version from '10.1'

[martinburchell]

@frafra I think if we were doing some serious development on this extension, we'd switch to GitHub actions.

We still use this extension on a CKAN 2.7 instance. If we were to move to a later CKAN version, we'd consider using https://github.com/datopian/ckanext-versions