pytest: remove flake8 warnings for tests/fixtures.py

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/fixtures.py

@@ -147,6 +147,7 @@ def teardown_checks(request):
         request.node.has_errors = True
         raise ValueError(str(errors))
 
+
 @pytest.fixture
 def node_factory(request, directory, test_name, bitcoind, executor, teardown_checks):
     nf = NodeFactory(
@@ -157,7 +158,6 @@ def node_factory(request, directory, test_name, bitcoind, executor, teardown_che
     )
 
     yield nf
-    err_count = 0
     ok, errs = nf.killall([not n.may_fail for n in nf.nodes])
 
     for e in errs: