Extract __*meta*__ from META_FILE.

def find_meta(meta):
    """
    Extract __*meta*__ from META_FILE.
    """
    meta_match = re.search(
        r"^__{meta}__ = ['\"]([^'\"]*)['\"]".format(meta=meta),
        META_FILE, re.M
    )
    if meta_match:
        return meta_match.group(1)
    raise RuntimeError("Unable to find __{meta}__ string.".format(meta=meta))