Write a test checking plugin failure exception handling

tests/unit/conftest.py

@@ -0,0 +1,17 @@
+"""Shared fixtures between unit tests"""
+import pytest
+import optparse
+
+def options_from(**kwargs):
+    """Generate a Values instances with our kwargs."""
+    kwargs.setdefault('hang_closing', True)
+    kwargs.setdefault('max_line_length', 79)
+    kwargs.setdefault('verbose', False)
+    kwargs.setdefault('stdin_display_name', 'stdin')
+    return optparse.Values(kwargs)
+
+@pytest.fixture
+def default_options():
+    """Fixture returning the default options of flake8"""
+    return options_from()
+