A simple function that takes a string representing an Indian phone number, and returns it in a canonical format '91dddddddddd'.

Usage:
        >>> from parsephoneno import canonical_number
        >>> canonical_number('98220-12345')
        919822012345
        >>> canonical_number('98220 1234')
        Traceback (most recent call last):
        ...
        NumberTooShortError: 982201234

        >>> phone_number('98220 1234') # Does not throw an exception
        >>>

See docstrings for more examples