Support parallel sphinx building

IPython/sphinxext/ipython_console_highlighting.py

@@ -13,7 +13,8 b' def setup(app):'
     # But if somebody knows what the right API usage should be to do that via
     # sphinx, by all means fix it here.  At least having this setup.py
     # suppresses the sphinx warning we'd get without it.
-    pass
+    metadata = {'parallel_read_safe': True, 'parallel_write_safe': True}
+    return metadata
 
 # Register the extension as a valid pygments lexer.
 # Alternatively, we could register the lexer with pygments instead. This would

IPython/sphinxext/ipython_directive.py

@@ -1008,6 +1008,9 b' def setup(app):'
 
     app.add_config_value('ipython_holdcount', True, 'env')
 
+    metadata = {'parallel_read_safe': True, 'parallel_write_safe': True}
+    return metadata
+
 # Simple smoke test, needs to be converted to a proper automatic test.
 def test():
 

docs/sphinxext/github.py

@@ -152,4 +152,6 b' def setup(app):'
     app.add_role('ghuser', ghuser_role)
     app.add_role('ghcommit', ghcommit_role)
     app.add_config_value('github_project_url', None, 'env')
-    return
+
+    metadata = {'parallel_read_safe': True, 'parallel_write_safe': True}
+    return metadata

docs/sphinxext/magics.py

@@ -40,3 +40,6 b' def setup(app):'
     StandardDomain.roles['magic'] = LineMagicRole()
     app.add_object_type('cellmagic', 'cellmagic', 'pair: %s; cell magic', parse_cell_magic)
     StandardDomain.roles['cellmagic'] = CellMagicRole()
+
+    metadata = {'parallel_read_safe': True, 'parallel_write_safe': True}
+    return metadata