issue_comments: 681605223

One solution would be to catch this ValueError, issue a FutureWarning and add allow_rechunk=True to dask_gufunc_kwargs here:

https://github.com/pydata/xarray/blob/9c85dd5f792805bea319f01f08ee51b83bde0f3b/xarray/core/computation.py#L646-L657

```python def func(*arrays): import dask.array as da

        gufunc = functools.partial(
            da.apply_gufunc,
            numpy_func,
            signature.to_gufunc_string(exclude_dims),
            *arrays,
            vectorize=vectorize,
            output_dtypes=output_dtypes,
        )

        try:
            res = gufunc(**dask_gufunc_kwargs)
        except ValueError as exc:
            if "with different chunksize present" in str(exc):
                warnings.warn(
                    f"``allow_rechunk=True`` need to be explicitely set in the "
                    f"``dask_gufunc_kwargs`` parameter. Not setting will raise dask "
                    f"ValueError ``{str(exc)}`` in a future version.",
                    FutureWarning,
                    stacklevel=2,
                )
                dask_gufunc_kwargs["allow_rechunk"] = True
                res = gufunc(**dask_gufunc_kwargs)
            else:
                raise

```

I could make a PR out of this. The message wording can surely be improved. WDYT @dcherian and @shoyer?