The repr of GenericMap raises an error if the WCS is an unknown type.

[Cadair]

Make a WCS with some nonsense in CTYPE1 CTYPE2 and then call repr(smap)

[Cadair]

In [1]: from sunpy.data.sample import AIA_171_IMAGE; import sunpy.map; import matplotlib.pyplot as plt

In [2]: m = sunpy.map.Map(AIA_171_IMAGE)

In [3]: m.meta['CTYPE1'] = "STUART1"

In [4]: m.meta['CTYPE2'] = "STUART2"

In [5]: m

Out[5]: ---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/opt/miniconda/envs/sunpy-dev/lib/python3.6/site-packages/IPython/core/formatters.py in __call__(self, obj)
    700                 type_pprinters=self.type_printers,
    701                 deferred_pprinters=self.deferred_printers)
--> 702             printer.pretty(obj)
    703             printer.flush()
    704             return stream.getvalue()

/opt/miniconda/envs/sunpy-dev/lib/python3.6/site-packages/IPython/lib/pretty.py in pretty(self, obj)
    393                             if callable(meth):
    394                                 return meth(obj, self, cycle)
--> 395             return _default_pprint(obj, self, cycle)
    396         finally:
    397             self.end_group()

/opt/miniconda/envs/sunpy-dev/lib/python3.6/site-packages/IPython/lib/pretty.py in _default_pprint(obj, p, cycle)
    508     if _safe_getattr(klass, '__repr__', None) is not object.__repr__:
    509         # A user-provided repr. Find newlines and replace them with p.break_()
--> 510         _repr_pprint(obj, p, cycle)
    511         return
    512     p.begin_group(1, '<')

/opt/miniconda/envs/sunpy-dev/lib/python3.6/site-packages/IPython/lib/pretty.py in _repr_pprint(obj, p, cycle)
    699     """A pprint that just redirects to the normal repr function."""
    700     # Find newlines and replace them with p.break_()
--> 701     output = repr(obj)
    702     for idx,output_line in enumerate(output.splitlines()):
    703         if idx:

~/Git/sunpy/sunpy/map/mapbase.py in __repr__(self)
    247            dim=u.Quantity(self.dimensions),
    248            scale=u.Quantity(self.scale),
--> 249            coord=self.coordinate_frame,
    250            refpix=u.Quantity(self.reference_pixel),
    251            refcoord=u.Quantity((self.reference_coordinate.data.lon,

~/Git/sunpy/sunpy/map/mapbase.py in coordinate_frame(self)
    305         information for this Map.
    306         """
--> 307         return astropy.wcs.utils.wcs_to_celestial_frame(self.wcs)
    308 
    309     def _as_mpl_axes(self):

~/Git/astropy/astropy/wcs/utils.py in wcs_to_celestial_frame(wcs)
    203             if frame is not None:
    204                 return frame
--> 205     raise ValueError("Could not determine celestial frame corresponding to "
    206                      "the specified WCS object")
    207 

ValueError: Could not determine celestial frame corresponding to the specified WCS object

From this error, it looks like it's the coordinate_frame property that needs the fix. I think it should probably return None if the lookup fails.

[talsperre]

I tried returning None if the lookup failed in coordinate_frame() function of mapbase.

try:
    return astropy.wcs.utils.wcs_to_celestial_frame(self.wcs)
except ValueError:
    return None

However, this leads to new errors such as AttributeError: 'NoneType' object has no attribute 'name' when calling repr(mapobj)