import re


def get_version_string(init_file):
    """
    Read __version__ string for an init file.
    """

    with open(init_file, 'r') as fp:
        content = fp.read()
        version_match = re.search(r"^__version__ = ['\"]([^'\"]*)['\"]",
                                  content, re.M)
        if version_match:
            return version_match.group(1)

        raise RuntimeError('Unable to find version string in %s.' % (init_file))