fix mypy errors

tests/unit/test_exceptions.py

@@ -1,48 +1,34 @@
 """Tests for the flake8.exceptions module."""
 import pickle
 
+import pytest
+
 from flake8 import exceptions
 
 
-class _ExceptionTest:
-    def test_pickleable(self):
-        """Test that the exception is round-trip pickleable."""
-        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
-            new_err = pickle.loads(pickle.dumps(self.err, protocol=proto))
-            assert str(self.err) == str(new_err)
-            orig_e = self.err.original_exception
-            new_e = new_err.original_exception
-            assert (type(orig_e), orig_e.args) == (type(new_e), new_e.args)
-
-
-class TestFailedToLoadPlugin(_ExceptionTest):
-    """Tests for the FailedToLoadPlugin exception."""
-
-    err = exceptions.FailedToLoadPlugin(
-        plugin_name='plugin_name',
-        exception=ValueError('boom!'),
-    )
-
-
-class TestInvalidSyntax(_ExceptionTest):
-    """Tests for the InvalidSyntax exception."""
-
-    err = exceptions.InvalidSyntax(exception=ValueError('Unexpected token: $'))
-
-
-class TestPluginRequestedUnknownParameters(_ExceptionTest):
-    """Tests for the PluginRequestedUnknownParameters exception."""
-
-    err = exceptions.PluginRequestedUnknownParameters(
-        plugin={'plugin_name': 'plugin_name'},
-        exception=ValueError('boom!'),
-    )
-
-
-class TestPluginExecutionFailed(_ExceptionTest):
-    """Tests for the PluginExecutionFailed exception."""
-
-    err = exceptions.PluginExecutionFailed(
-        plugin={'plugin_name': 'plugin_name'},
-        exception=ValueError('boom!'),
-    )
+@pytest.mark.parametrize(
+    'err',
+    (
+        exceptions.FailedToLoadPlugin(
+            plugin_name='plugin_name',
+            exception=ValueError('boom!'),
+        ),
+        exceptions.InvalidSyntax(exception=ValueError('Unexpected token: $')),
+        exceptions.PluginRequestedUnknownParameters(
+            plugin={'plugin_name': 'plugin_name'},
+            exception=ValueError('boom!'),
+        ),
+        exceptions.PluginExecutionFailed(
+            plugin={'plugin_name': 'plugin_name'},
+            exception=ValueError('boom!'),
+        )
+    ),
+)
+def test_pickleable(err):
+    """Ensure that our exceptions can cross pickle boundaries."""
+    for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+        new_err = pickle.loads(pickle.dumps(err, protocol=proto))
+        assert str(err) == str(new_err)
+        orig_e = err.original_exception
+        new_e = new_err.original_exception
+        assert (type(orig_e), orig_e.args) == (type(new_e), new_e.args)