html repr fails on non-str Dataset keys

[max-sixty]

MCVE Code Sample

# In a notebook with html repr enabled
xr.Dataset({0: (('a','b'), np.random.rand(2,3))})

# gives:


---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
/j/office/app/research-python/conda/envs/2019.10/lib/python3.7/site-packages/IPython/core/formatters.py in __call__(self, obj)
    343             method = get_real_method(obj, self.print_method)
    344             if method is not None:
--> 345                 return method()
    346             return None
    347         else:

~/.local/lib/python3.7/site-packages/xarray/core/dataset.py in _repr_html_(self)
   1632         if OPTIONS["display_style"] == "text":
   1633             return f"<pre>{escape(repr(self))}</pre>"
-> 1634         return formatting_html.dataset_repr(self)
   1635 
   1636     def info(self, buf=None) -> None:

~/.local/lib/python3.7/site-packages/xarray/core/formatting_html.py in dataset_repr(ds)
    268         dim_section(ds),
    269         coord_section(ds.coords),
--> 270         datavar_section(ds.data_vars),
    271         attr_section(ds.attrs),
    272     ]

~/.local/lib/python3.7/site-packages/xarray/core/formatting_html.py in _mapping_section(mapping, name, details_func, max_items_collapse, enabled)
    165     return collapsible_section(
    166         name,
--> 167         details=details_func(mapping),
    168         n_items=n_items,
    169         enabled=enabled,

~/.local/lib/python3.7/site-packages/xarray/core/formatting_html.py in summarize_vars(variables)
    131     vars_li = "".join(
    132         f"<li class='xr-var-item'>{summarize_variable(k, v)}</li>"
--> 133         for k, v in variables.items()
    134     )
    135 

~/.local/lib/python3.7/site-packages/xarray/core/formatting_html.py in <genexpr>(.0)
    131     vars_li = "".join(
    132         f"<li class='xr-var-item'>{summarize_variable(k, v)}</li>"
--> 133         for k, v in variables.items()
    134     )
    135 

~/.local/lib/python3.7/site-packages/xarray/core/formatting_html.py in summarize_variable(name, var, is_index, dtype, preview)
     96     cssclass_idx = " class='xr-has-index'" if is_index else ""
     97     dims_str = f"({', '.join(escape(dim) for dim in var.dims)})"
---> 98     name = escape(name)
     99     dtype = dtype or escape(str(var.dtype))
    100 

/j/office/app/research-python/conda/envs/2019.10/lib/python3.7/html/__init__.py in escape(s, quote)
     17     translated.
     18     """
---> 19     s = s.replace("&", "&amp;") # Must be done first!
     20     s = s.replace("<", "&lt;")
     21     s = s.replace(">", "&gt;")

AttributeError: 'int' object has no attribute 'replace'

<xarray.Dataset>
Dimensions:  (a: 2, b: 3)
Dimensions without coordinates: a, b
Data variables:
    0        (a, b) float64 0.5327 0.927 0.8582 0.8825 0.9478 0.09475

Problem Description

I think this may be an uncomplicated fix: coerce the keys to str

Output of xr.show_versions()

INSTALLED VERSIONS ------------------ commit: None python: 3.7.3 | packaged by conda-forge | (default, Jul 1 2019, 21:52:21) [GCC 7.3.0] python-bits: 64 OS: Linux OS-release: ... machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.utf8 LOCALE: en_US.UTF-8 libhdf5: 1.10.5 libnetcdf: 4.7.1

xarray: 0.15.0
pandas: 1.0.1
numpy: 1.17.3
scipy: 1.3.2
netCDF4: 1.5.3
pydap: None
h5netcdf: 0.7.4
h5py: 2.10.0
Nio: None
zarr: None
cftime: 1.0.4.2
nc_time_axis: None
PseudoNetCDF: None
rasterio: None
cfgrib: None
iris: None
bottleneck: 1.2.1
dask: 2.7.0
distributed: 2.7.0
matplotlib: 3.1.2
cartopy: None
seaborn: 0.9.0
numbagg: installed
setuptools: 41.6.0.post20191101
pip: 19.3.1
conda: None
pytest: 5.2.2
IPython: 7.9.0
sphinx: 2.2.1