Fixed E303 flake8 errors

too many blank lines (3)

testing/acceptance_test.py

@@ -81,7 +81,6 @@ class TestGeneralUsage(object):
             "*---unconfigure",
         ])
 
-
     def test_config_preparse_plugin_option(self, testdir):
         testdir.makepyfile(pytest_xyz="""
             def pytest_addoption(parser):
@@ -147,7 +146,6 @@ class TestGeneralUsage(object):
             *ERROR*could not load*conftest.py*
         """)
 
-
     def test_early_skip(self, testdir):
         testdir.mkdir("xyz")
         testdir.makeconftest("""
@@ -676,7 +674,6 @@ class TestInvocationVariants(object):
         import _pytest.config
         assert type(_pytest.config.get_plugin_manager()) is _pytest.config.PytestPluginManager
 
-
     def test_has_plugin(self, request):
         """Test hasplugin function of the plugin manager (#932)."""
         assert request.config.pluginmanager.hasplugin('python')