def read_release_version():
    """Read the release version from ``_version.py``."""
    import re
    dirname = os.path.abspath(os.path.dirname(__file__))

    try:
        f = open(os.path.join(dirname, "_version.py"), "rt")
        for line in f.readlines():

            m = re.match("__version__ = '([^']+)'", line)
            if m:
                ver = m.group(1)
                return ver

    except:
        return None

    return None
Read the release version from ``_version.py``.