bpo-31787: Skip refleak check when _hashlib is not available (GH-5660)

bpo-31787: Skip refleak check when _hashlib is not available (GH-5660) · python/cpython@f0bc645

Original file line number	Diff line number	Diff line change
`@@ -163,6 +163,7 @@ def hash_constructors(self):`
`163`	`163`	`return itertools.chain.from_iterable(constructors)`
`164`	`164`
`165`	`165`	`@support.refcount_test`
	`166`	`+@unittest.skipIf(c_hashlib is None, 'Require _hashlib module')`
`166`	`167`	`def test_refleaks_in_hash___init__(self):`
`167`	`168`	`gettotalrefcount = support.get_attribute(sys, 'gettotalrefcount')`
`168`	`169`	`sha1_hash = c_hashlib.new('sha1')`