Dear Wikibase experts,

I have a (hopefully) trivial question to ask: is there any specific configuration to set in order to make a wikibase extension accessible via libraries such as Pywikibot? 
Should I maybe activate the wikibase_client ?

Here's the problem described from the Pywikibot point of view: when I try to connect to my wikibase installation, I can access the mediawiki pages...
In [1]: import pywikibot
In [2]: site = pywikibot.Site()
In [9]: page = pywikibot.Page(site, u"Main_Page")
In [10]: page.get()
Out[10]: u"<strong>MediaWiki ha ........................

...but I cannot access the wikibase Items (created in the same mediawiki installation), since the "site.data_repository()" method (of my local Pywikibot site-object) returns an EMPTY value...
In [37]: site.data_repository()
In [38]: type(site.data_repository())
Out[38]: NoneType

While, if I access (the same way) the wikibase instance of https://test.wikidata.org (of course) I get a correct response from the "site.data_repository()" method (of my local Pywikibot site-object):
In [39]: wikidatatest_site = pywikibot.Site("test", "wikidata")
In [40]: wikidatatest_site.data_repository()
Out[40]: DataSite("test", "wikidata")
In [41]: type(wikidatatest_site.data_repository())
Out[41]: pywikibot.site.DataSite

Here are the main details of my mediawiki/wikibase installation:
- MediaWiki: 1.26.2
- PHP: 5.6.15 (apache2handler)
- MariaDB: 10.1.9-MariaDB
- ICU: 4.8.1.1
...with these extensions (with specific versions) for Wikibase:
- Purtle: 0.1-dev
- Wikibase DataModel: 4.4.0
- Wikibase DataModel JavaScript: 1.0.2-dev
- Wikibase DataModel Serialization: 2.1.0
- Wikibase Internal Serialization: 2.1.0
- Wikibase JavaScript API: 1.1.0
- Wikibase Repository: 0.5 alpha (32d7ef0) 00:03, 30 September 2015
- Wikibase Serialization JavaScript: 2.0.6
- Wikibase View: 0.1-dev
- WikibaseLib: 0.5 alpha (32d7ef0) 00:03, 30 September 2015

If this question is asked in the wrong context I'm really sorry (I searched with no success the official pages of Wikibase and the archive of this mailing-list, http://blog.gmane.org/gmane.org.wikimedia.wikidata.technical): 
please let me know whether I should better ask this question to the Pywikibot library guys.

Thanks a lot for attention!