use pytest.fixture instead of yield_fixture, fixes borgbackup#5575

/vagrant/borg/borg/.tox/py36-none/lib/python3.6/site-packages/borg/testsuite/remote.py:73:
    PytestDeprecationWarning: @pytest.yield_fixture is deprecated.
Use @pytest.fixture instead; they are the same.
Docs: https://docs.pytest.org/en/stable/warnings.html

src/borg/testsuite/benchmark.py

@@ -13,7 +13,7 @@
 from .archiver import changedir, cmd
 
 
-@pytest.yield_fixture
+@pytest.fixture
 def repo_url(request, tmpdir, monkeypatch):
     monkeypatch.setenv('BORG_PASSPHRASE', '123456')
     monkeypatch.setenv('BORG_CHECK_I_KNOW_WHAT_I_AM_DOING', 'YES')
@@ -31,7 +31,7 @@ def repo(request, cmd, repo_url):
     return repo_url
 
 
-@pytest.yield_fixture(scope='session', params=["zeros", "random"])
+@pytest.fixture(scope='session', params=["zeros", "random"])
 def testdata(request, tmpdir_factory):
     count, size = 10, 1000*1000
     p = tmpdir_factory.mktemp('data')

src/borg/testsuite/cache.py

@@ -208,7 +208,7 @@ def test_refcount_one_below_max_value(self):
 
 
 class TestAdHocCache:
-    @pytest.yield_fixture
+    @pytest.fixture
     def repository(self, tmpdir):
         self.repository_location = os.path.join(str(tmpdir), 'repository')
         with Repository(self.repository_location, exclusive=True, create=True) as repository:

src/borg/testsuite/remote.py

@@ -70,7 +70,7 @@ def test_write(self, monkeypatch):
 
 
 class TestRepositoryCache:
-    @pytest.yield_fixture
+    @pytest.fixture
     def repository(self, tmpdir):
         self.repository_location = os.path.join(str(tmpdir), 'repository')
         with Repository(self.repository_location, exclusive=True, create=True) as repository: