replace system errors (#529)

This PR replaces Envisage's uses of `SystemError` with more appropriate
exceptions.

Closes #442

---------

Co-authored-by: Chengyu Liu <cyliu@aus552cyliu.local>

envisage/composite_plugin_manager.py

@@ -155,7 +155,7 @@ def start_plugin(self, plugin=None, plugin_id=None):
             logger.debug("plugin %s started", plugin.id)
 
         else:
-            raise SystemError("no such plugin %s" % plugin_id)
+            raise ValueError("no such plugin %s" % plugin_id)
 
     def stop(self):
         """ Stop the plugin manager. """
@@ -177,4 +177,4 @@ def stop_plugin(self, plugin=None, plugin_id=None):
             logger.debug("plugin %s stopped", plugin.id)
 
         else:
-            raise SystemError("no such plugin %s" % plugin_id)
+            raise ValueError("no such plugin %s" % plugin_id)

envisage/egg_basket_plugin_manager.py

@@ -153,7 +153,7 @@ def _harvest_plugins_in_eggs(self, application):
     def _handle_broken_distributions(self, errors):
         logger.error("Error loading distributions: %s", errors)
         if self.on_broken_distribution is None:
-            raise SystemError("Cannot find eggs %s" % errors)
+            raise RuntimeError("Cannot find eggs %s" % errors)
         else:
             for dist, exc in errors.items():
                 self.on_broken_distribution(dist, exc)

envisage/egg_utils.py

@@ -29,7 +29,7 @@ def add_eggs_on_path(working_set, path, on_error=None):
         if on_error:
             on_error(errors)
         else:
-            raise SystemError("Cannot find eggs %s" % errors)
+            raise RuntimeError("Cannot find eggs %s" % errors)
 
     # Add the distributions to the working set (this makes any Python
     # modules in the eggs available for importing).

envisage/i_plugin_manager.py

@@ -63,7 +63,7 @@ def start_plugin(self, plugin=None, plugin_id=None):
         If a plugin is specified then start it.
 
         If no plugin is specified then the Id is used to look up the plugin
-        and then start it. If no such plugin exists then a 'SystemError'
+        and then start it. If no such plugin exists then a 'ValueError'
         exception is raised.
 
         """
@@ -82,7 +82,7 @@ def stop_plugin(self, plugin=None, plugin_id=None):
         If a plugin is specified then stop it (the Id is ignored).
 
         If no plugin is specified then the Id is used to look up the plugin and
-        then stop it. If no such plugin exists then a 'SystemError' exception
+        then stop it. If no such plugin exists then a 'ValueError' exception
         is raised.
 
         """

envisage/plugin_manager.py

@@ -144,7 +144,7 @@ def start_plugin(self, plugin=None, plugin_id=None):
             logger.debug("plugin %s started", plugin.id)
 
         else:
-            raise SystemError("no such plugin %s" % plugin_id)
+            raise ValueError("no such plugin %s" % plugin_id)
 
     def stop(self):
         """ Stop the plugin manager. """
@@ -166,7 +166,7 @@ def stop_plugin(self, plugin=None, plugin_id=None):
             logger.debug("plugin %s stopped", plugin.id)
 
         else:
-            raise SystemError("no such plugin %s" % plugin_id)
+            raise ValueError("no such plugin %s" % plugin_id)
 
     #### Protected 'PluginManager' ############################################
 

envisage/provider_extension_registry.py

@@ -42,7 +42,7 @@ class ProviderExtensionRegistry(ExtensionRegistry):
     def set_extensions(self, extension_point_id, extensions):
         """ Set the extensions to an extension point. """
 
-        raise SystemError("extension points cannot be set")
+        raise TypeError("extension points cannot be set")
 
     ###########################################################################
     # 'ProviderExtensionRegistry' interface.

envisage/service.py

@@ -14,8 +14,7 @@
 import logging
 
 # Enthought library imports.
-from traits.api import TraitType
-
+from traits.api import TraitError, TraitType
 
 # Logging.
 logger = logging.getLogger(__name__)
@@ -74,7 +73,7 @@ def get(self, obj, trait_name):
     def set(self, obj, name, value):
         """ Trait type setter. """
 
-        raise SystemError("Service traits cannot be set")
+        raise TraitError("Service traits cannot be set")
 
     ###########################################################################
     # Private interface.

envisage/tests/test_application.py

@@ -285,11 +285,11 @@ def test_start_and_stop_errors(self):
             application.stop()
 
         # Try to start a non-existent plugin.
-        with self.assertRaises(SystemError):
+        with self.assertRaises(ValueError):
             application.start_plugin(plugin_id="bogus")
 
         # Try to stop a non-existent plugin.
-        with self.assertRaises(SystemError):
+        with self.assertRaises(ValueError):
             application.stop_plugin(plugin_id="bogus")
 
     def test_extension_point(self):

envisage/tests/test_egg_based.py

@@ -118,7 +118,7 @@ def _add_eggs_on_path(self, path, working_set=None):
         # Py2 tests was checking that len(errors) > 0. This did not work on
         # Py3. Test changed to check the len(distributions)
         if len(distributions) == 0:
-            raise SystemError("Cannot find eggs %s" % errors)
+            raise RuntimeError("Cannot find eggs %s" % errors)
 
         # Add the distributions to the working set (this makes any Python
         # modules in the eggs available for importing).

envisage/tests/test_egg_basket_plugin_manager.py

@@ -215,7 +215,7 @@ def test_ignore_broken_distributions_raises_exceptions_by_default(self):
                 self._create_broken_distribution_eggdir("acme.foo*.egg"),
             ],
         )
-        with self.assertRaises(SystemError):
+        with self.assertRaises(RuntimeError):
             iter(plugin_manager)
 
     def test_ignore_broken_distributions_loads_good_distributions(self):

envisage/tests/test_extension_point_changed.py

@@ -44,7 +44,7 @@ def test_set_extension_point(self):
         application.start()
 
         # Try to set the extension point.
-        with self.assertRaises(SystemError):
+        with self.assertRaises(TypeError):
             setattr(a, "x", [1, 2, 3])
 
     def test_mutate_extension_point_no_events(self):

envisage/tests/test_plugin_manager.py

@@ -130,11 +130,11 @@ def test_start_and_stop_errors(self):
             plugin_manager.stop()
 
         # Try to start a non-existent plugin.
-        with self.assertRaises(SystemError):
+        with self.assertRaises(ValueError):
             plugin_manager.start_plugin(plugin_id="bogus")
 
         # Try to stop a non-existent plugin.
-        with self.assertRaises(SystemError):
+        with self.assertRaises(ValueError):
             plugin_manager.stop_plugin(plugin_id="bogus")
 
     def test_only_include_plugins_whose_ids_are_in_the_include_list(self):

envisage/tests/test_provider_extension_registry.py

@@ -523,7 +523,7 @@ def test_set_extensions(self):
         registry.add_extension_point(self.create_extension_point("my.ep"))
 
         # Set some extensions.
-        with self.assertRaises(SystemError):
+        with self.assertRaises(TypeError):
             registry.set_extensions("my.ep", [1, 2, 3])
 
     def test_remove_non_empty_extension_point(self):

envisage/tests/test_service.py

@@ -14,7 +14,7 @@
 
 # Enthought library imports.
 from envisage.api import Application, Plugin, Service
-from traits.api import HasTraits, Instance
+from traits.api import HasTraits, Instance, TraitError
 
 
 class TestApplication(Application):
@@ -56,7 +56,7 @@ class PluginB(Plugin):
         self.assertEqual(None, b.foo)
 
         # You can't set service traits!
-        with self.assertRaises(SystemError):
+        with self.assertRaises(TraitError):
             setattr(b, "foo", "bogus")
 
     def test_service_trait_type_with_no_service_registry(self):

examples/legacy/MOTD_Using_Eggs/dist/run.py

@@ -73,7 +73,7 @@ def main():
 
     distributions, errors = working_set.find_plugins(environment)
     if len(errors) > 0:
-        raise SystemError('cannot add eggs %s' % errors)
+        raise RuntimeError('cannot add eggs %s' % errors)
 
     logger.debug('added eggs %s' % distributions)
 

examples/legacy/plugins/workbench/AcmeLab/acme/workbench/view/color_view.py

@@ -45,7 +45,7 @@ def create_control(self, parent):
 
         method = getattr(self, "_%s_create_control" % ETSConfig.toolkit, None)
         if method is None:
-            raise SystemError("Unknown toolkit %s", ETSConfig.toolkit)
+            raise RuntimeError("Unknown toolkit %s", ETSConfig.toolkit)
 
         color = self.name.lower()
 

examples/legacy/plugins/workbench/AcmeLabUsingEggs/dist/run.py

@@ -68,7 +68,7 @@ def main():
 
     distributions, errors = working_set.find_plugins(environment)
     if len(errors) > 0:
-        raise SystemError('cannot add eggs %s' % errors)
+        raise RuntimeError('cannot add eggs %s' % errors)
 
     logger.debug('added eggs %s' % distributions)
 

examples/legacy/plugins/workbench/AcmeLabUsingEggs/src/acme.workbench/acme/workbench/view/color_view.py

@@ -45,7 +45,7 @@ def create_control(self, parent):
 
         method = getattr(self, "_%s_create_control" % ETSConfig.toolkit, None)
         if method is None:
-            raise SystemError("Unknown toolkit %s", ETSConfig.toolkit)
+            raise RuntimeError("Unknown toolkit %s", ETSConfig.toolkit)
 
         color = self.name.lower()