astropy: IERS error when converting to altaz

When writing this code with Python 3.6 and Astropy v2.0.2:

from astropy import coordinates as coord
import astropy.units as u
from astropy import time

vega = coord.SkyCoord.from_name('Vega')

loc = coord.EarthLocation(lon=0.1 * u.deg,
                          lat=51.5 * u.deg)

obstime = time.Time(57734.1231, format='mjd')

altaz = coord.AltAz(location=loc, obstime=obstime)

vega_altaz = vega.transform_to(altaz)

I get this error:

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/io/ascii/core.py in _convert_vals(self, cols)
    956                 try:
--> 957                     converter_func, converter_type = col.converters[0]
    958                     if not issubclass(converter_type, col.type):

IndexError: list index out of range

During handling of the above exception, another exception occurred:

ValueError                                Traceback (most recent call last)
<ipython-input-23-5540b2e880c6> in <module>()
     10 altaz = coord.AltAz(location=loc, obstime=time)
     11 
---> 12 vega_altaz = vega.transform_to(altaz)
     13 vega_altaz.alt

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/coordinates/sky_coordinate.py in transform_to(self, frame, merge_attributes)
    479         # Do the transformation, returning a coordinate frame of the desired
    480         # final type (not generic).
--> 481         new_coord = trans(self.frame, generic_frame)
    482 
    483         # Finally make the new SkyCoord object from the `new_coord` and

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/coordinates/transformations.py in __call__(self, fromcoord, toframe)
   1312 
   1313             curr_toframe = t.tosys(**frattrs)
-> 1314             curr_coord = t(curr_coord, curr_toframe)
   1315 
   1316         # this is safe even in the case where self.transforms is empty, because

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/coordinates/transformations.py in __call__(self, fromcoord, toframe)
    912             return reprwithoutdiff.realize_frame(reprwithdiff)
    913         else:
--> 914             return supcall(fromcoord, toframe)
    915 
    916 

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/coordinates/builtin_frames/cirs_observed_transforms.py in cirs_to_altaz(cirs_coo, altaz_frame)
     51 
     52     lon, lat, height = altaz_frame.location.to_geodetic('WGS84')
---> 53     xp, yp = get_polar_motion(obstime)
     54 
     55     # first set up the astrometry context for CIRS<->AltAz

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/coordinates/builtin_frames/utils.py in get_polar_motion(time)
     41     """
     42     # Get the polar motion from the IERS table
---> 43     xp, yp, status = iers.IERS_Auto.open().pm_xy(time, return_status=True)
     44 
     45     wmsg = None

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/utils/iers/iers.py in open(cls)
    586             return cls.iers_table
    587 
--> 588         cls.iers_table = cls.read(file=filename)
    589         cls.iers_table.meta['data_url'] = str(conf.iers_auto_url)
    590 

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/utils/iers/iers.py in read(cls, file, readme)
    455         # Read in as a regular Table, including possible masked columns.
    456         # Columns will be filled and converted to Quantity in cls.__init__.
--> 457         iers_a = Table.read(file, format='cds', readme=readme)
    458 
    459         # Combine the A and B data for UT1-UTC and PM columns

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/table/table.py in read(cls, *args, **kwargs)
   2519         passed through to the underlying data reader (e.g. `~astropy.io.ascii.read`).
   2520         """
-> 2521         out = io_registry.read(cls, *args, **kwargs)
   2522         # For some readers (e.g., ascii.ecsv), the returned `out` class is not
   2523         # guaranteed to be the same as the desired output `cls`.  If so,

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/io/registry.py in read(cls, *args, **kwargs)
    529 
    530         reader = get_reader(format, cls)
--> 531         data = reader(*args, **kwargs)
    532 
    533         if not isinstance(data, cls):

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/io/ascii/connect.py in io_read(format, filename, **kwargs)
     37     from .ui import read
     38     format = re.sub(r'^ascii\.', '', format)
---> 39     return read(filename, format=format, **kwargs)
     40 
     41 

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/io/ascii/ui.py in read(table, guess, **kwargs)
    351                                              ' with fast (no guessing)'})
    352         else:
--> 353             dat = reader.read(table)
    354             _read_trace.append({'kwargs': new_kwargs,
    355                                 'status': 'Success with specified Reader class '

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/io/ascii/cds.py in read(self, table)
    320                     return table
    321         else:
--> 322             return super(Cds, self).read(table)

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/io/ascii/core.py in read(self, table)
   1200         if hasattr(self.header, 'table_meta'):
   1201             self.meta['table'].update(self.header.table_meta)
-> 1202         table = self.outputter(cols, self.meta)
   1203         self.cols = self.header.cols
   1204 

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/io/ascii/core.py in __call__(self, cols, meta)
    986         # Sets col.data to numpy array and col.type to io.ascii Type class (e.g.
    987         # FloatType) for each col.
--> 988         self._convert_vals(cols)
    989 
    990         # If there are any values that were filled and tagged with a mask bit then this

/Users/elliannaschwab/anaconda/lib/python3.6/site-packages/astropy/io/ascii/core.py in _convert_vals(self, cols)
    971                     last_err = err
    972                 except IndexError:
--> 973                     raise ValueError('Column {} failed to convert: {}'.format(col.name, last_err))
    974 
    975 

ValueError: Column year failed to convert: invalid literal for int() with base 10: '<h'