Take a string and a filename path string and return the found value.

def find_this(search, source=SOURCE):
    """Take a string and a filename path string and return the found value."""
    print("Searching for {what}.".format(what=search))
    if not search or not source:
        print("Not found on source: {what}.".format(what=search))
        return ""
    return str(re.compile(r'.*__{what}__ = "(.*?)"'.format(
        what=search), re.S).match(source).group(1)).strip()