Problems with not having exceptions crash my script

[Gribouillis]

I'm not sure whether I should shelve exception handling until I've got the more important and interesting parts of the application complete. What do you think?

If you write a function named validate_scheme(), it means that you are now and then expecting invalid urls. The case where an error occurs in this call can be incorporated to this invalid case.

In your situation, I would create my own exception type InvalidUrl and raise this exception

class InvalidUrl(Exception): pass

def split_url(url):
    """Splits url for other validation functions.
 
        :returns:       urllib.split.urlsplit object
    """
    try:
        return urllib.parse.urlsplit(url)
    except Exception as exc:
        raise InvalidUrl from exc

def validate_scheme(split_url):
    """Validates schema of url against a limited list of valid schemas.
    """
    if split_url.scheme in schemes:
        return split_url
    else:
        raise InvalidUrl(("Invalid url scheme", split_url.scheme, "must be one of", schemes))

Now the code that uses this can catch InvalidUrl and take corrective action when an invalid url is met.