Reduce dupe between tests.py and matplotlib.test

Fix matplotlib#5328

lib/matplotlib/__init__.py

@@ -1487,7 +1487,14 @@ def tk_window_focus():
     ]
 
 
-def verify_test_dependencies():
+def _init_tests():
+    try:
+        import faulthandler
+    except ImportError:
+        pass
+    else:
+        faulthandler.enable()
+
     if not os.path.isdir(os.path.join(os.path.dirname(__file__), 'tests')):
         raise ImportError("matplotlib test data is not installed")
 
@@ -1502,28 +1509,27 @@ def verify_test_dependencies():
         raise
 
 
+def _get_extra_test_plugins():
+    from .testing.noseclasses import KnownFailure
+    from nose.plugins import attrib
+
+    return [KnownFailure(), attrib.Plugin()]
+
+
 def test(verbosity=1):
     """run the matplotlib test suite"""
-    verify_test_dependencies()
-    try:
-        import faulthandler
-    except ImportError:
-        pass
-    else:
-        faulthandler.enable()
+    _init_tests()
 
     old_backend = rcParams['backend']
     try:
         use('agg')
         import nose
         import nose.plugins.builtin
-        from .testing.noseclasses import KnownFailure
         from nose.plugins.manager import PluginManager
         from nose.plugins import multiprocess
 
         # store the old values before overriding
-        plugins = []
-        plugins.append(KnownFailure())
+        plugins = _get_extra_test_plugins()
         plugins.extend([plugin() for plugin in nose.plugins.builtin.plugins])
 
         manager = PluginManager(plugins=plugins)
@@ -1532,7 +1538,7 @@ def test(verbosity=1):
         # Nose doesn't automatically instantiate all of the plugins in the
         # child processes, so we have to provide the multiprocess plugin with
         # a list.
-        multiprocess._instantiate_plugins = [KnownFailure]
+        multiprocess._instantiate_plugins = plugins
 
         success = nose.run(
             defaultTest=default_test_modules,

tests.py

@@ -17,32 +17,21 @@
 matplotlib.use('agg')
 
 import nose
-from nose.plugins import attrib
-from matplotlib.testing.noseclasses import KnownFailure
 from matplotlib import default_test_modules
 
-plugins = [KnownFailure, attrib.Plugin]
-
-# Nose doesn't automatically instantiate all of the plugins in the
-# child processes, so we have to provide the multiprocess plugin with
-# a list.
-from nose.plugins import multiprocess
-multiprocess._instantiate_plugins = plugins
-
 
 def run(extra_args):
-    try:
-        import faulthandler
-    except ImportError:
-        pass
-    else:
-        faulthandler.enable()
+    from nose.plugins import multiprocess
+
+    matplotlib._init_tests()
 
-    if not os.path.isdir(
-            os.path.join(os.path.dirname(matplotlib.__file__), 'tests')):
-        raise ImportError("matplotlib test data is not installed")
+    # Nose doesn't automatically instantiate all of the plugins in the
+    # child processes, so we have to provide the multiprocess plugin with
+    # a list.
+    plugins = matplotlib._get_extra_test_plugins()
+    multiprocess._instantiate_plugins = plugins
 
-    nose.main(addplugins=[x() for x in plugins],
+    nose.main(addplugins=plugins,
               defaultTest=default_test_modules,
               argv=sys.argv + extra_args)