import pywikibot

SITE = pywikibot.Site('wikidata', 'wikidata')
REPO = SITE.data_repository()
SANDBOX_1_QID = 'Q4115189'

catalog_pid = 'P2002'
catalog_id = 'bulgrozaz'
item = pywikibot.ItemPage(REPO, SANDBOX_1_QID)
claims = item.get()['claims']
identifier_claims = claims[catalog_pid]
for claim in identifier_claims:
    if claim.getTarget() == catalog_id:
        item.removeClaims([claim], summary='Test summary')
Sleeping for 7.9 seconds, 2018-09-25 10:46:06