issues: 168876028

If an AttributeError is raised at construction time by the accessor, it will be ignored silently:

``` python import xarray as xr

@xr.register_dataset_accessor('stupid_accessor') class GeoAccessor(object): def init(self, xarray_obj): self._obj = xarray_obj
raise AttributeError('Ups')

def plot(self):
    """Plot data on a map."""
    return 'plotting!'

ds = xr.Dataset({'longitude': np.linspace(0, 10), 'latitude': np.linspace(0, 20)}) ds.stupid_accessor.plot() ```

Will raise:

``` AttributeError Traceback (most recent call last) <ipython-input-1-b47ffc33cff2> in <module>() 12 13 ds = xr.Dataset({'longitude': np.linspace(0, 10), 'latitude': np.linspace(0, 20)}) ---> 14 ds.stupid_accessor.plot()

/home/mowglie/.pyvirtualenvs/py3/lib/python3.4/site-packages/xarray/core/common.py in getattr(self, name) 192 return source[name] 193 raise AttributeError("%r object has no attribute %r" % --> 194 (type(self).name, name)) 195 196 def setattr(self, name, value):

AttributeError: 'Dataset' object has no attribute 'stupid_accessor' ```

The problem with this error message is that it doesn't tell you that the problem is in your code.

Interestingly, raising other exceptions like RuntimeError will result in the more informative traceback:

``` RuntimeError Traceback (most recent call last) <ipython-input-1-b575d0257332> in <module>() 12 13 ds = xr.Dataset({'longitude': np.linspace(0, 10), 'latitude': np.linspace(0, 20)}) ---> 14 ds.stupid_accessor.plot()

/home/mowglie/.pyvirtualenvs/py3/lib/python3.4/site-packages/xarray/core/extensions.py in get(self, obj, cls) 17 # we're accessing the attribute of the class, i.e., Dataset.geo 18 return self._accessor ---> 19 accessor_obj = self._accessor(obj) 20 # Replace the property with the accessor object. Inspired by: 21 # http://www.pydanny.com/cached-property.html

<ipython-input-1-b575d0257332> in init(self, xarray_obj) 5 def init(self, xarray_obj): 6 self._obj = xarray_obj ----> 7 raise RuntimeError('Ups') 8 9 def plot(self):

RuntimeError: Ups ```