Use betterhelp easy mains to get parser off the global.

epubfile.py

@@ -1654,6 +1654,7 @@ def normalize_argparse(args):
         book.move_nav_to_end()
         book.save(epub)
 
+def main(argv):
     parser = argparse.ArgumentParser(description=__doc__)
     subparsers = parser.add_subparsers()
 
@@ -1693,10 +1694,12 @@ p_normalize = subparsers.add_parser('normalize')
     p_normalize.add_argument('epubs', nargs='+', default=[])
     p_normalize.set_defaults(func=normalize_argparse)
 
-@betterhelp.subparser_betterhelp(parser, main_docstring=DOCSTRING, sub_docstrings=SUB_DOCSTRINGS)
-def main(argv):
-    args = parser.parse_args(argv)
-    return args.func(args)
+    return betterhelp.subparser_main(
+        argv,
+        parser,
+        main_docstring=DOCSTRING,
+        sub_docstrings=SUB_DOCSTRINGS,
+    )
 
 if __name__ == '__main__':
     raise SystemExit(main(sys.argv[1:]))