help display main.py instead of ezchlog in usage

I run ezchlog like this:

$ python -m ezchlog commit --help
Commit using part changelog files content

usage: __main__.py commit [-h] [partlog]

positional arguments:
  partlog     Main part log path if this is ambiguous

options:
  -h, --help  show this help message and exit

I expect to have "usage: ezchlog commit [-h] [partlog]" instead