Given a string that is a number and a unit, return a
        Quantity of that string.Raise an Error If there is no unit.  e.g.:
            50" -> 50*u.arcsec
            50 -> CRTFRegionParserError : Units must be specified for 50

def parse_angular_length_quantity(string_rep):
        """
        Given a string that is a number and a unit, return a
        Quantity of that string.Raise an Error If there is no unit.  e.g.:
            50" -> 50*u.arcsec
            50 -> CRTFRegionParserError : Units must be specified for 50
        """
        unit_mapping = {
            'deg': u.deg,
            'rad': u.rad,
            'arcmin': u.arcmin,
            'arcsec': u.arcsec,
            'pix': u.dimensionless_unscaled,
            '"': u.arcsec,
            "'": u.arcmin,
        }
        regex_str = re.compile(r'([0-9+,-.]*)(.*)')
        str = regex_str.search(string_rep)
        unit = str.group(2)
        if unit:
            if unit in unit_mapping:
                return u.Quantity(str.group(1), unit=unit_mapping[unit])
            return u.Quantity(str.group(1))
        else:
            raise CRTFRegionParserError('Units must be specified for {0} '.format(string_rep))