Say my project has a Writer class in the file a/b/c.py. I can not refer to this writer using get_writer_class('a.b.c') because get_writer_class uses __import__ for importing the module and __import__('a.b.c') returns a in this case. Using importlib.import_module instead of __import__ would fix this and it is also the way that the help message for __import__ recommends.
Implemented in revision 8478.
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Fixed in Docutils 0.17.
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