fixed pep8 issues

Author: Lily Wang

xarray/backends/zarr.py

@@ -136,10 +136,10 @@ def _determine_zarr_chunks(enc_chunks, var_chunks, ndim):
                         % (enc_chunks_tuple, var_chunks))
             if dchunks[-1] > zchunk:
                 raise ValueError(
-                    "Final chunk of Zarr array must be the same size or smaller "
-                    "than the first. The specified Zarr chunk encoding is %r, "
-                    "but %r in variable Dask chunks %r is incompatible. "
-                    "Consider rechunking using `chunk()`." 
+                    "Final chunk of Zarr array must be the same size or "
+                    "smaller than the first. The specified Zarr chunk "
+                    "encoding is %r, but %r in variable Dask chunks %r is "
+                    "incompatible. Consider rechunking using `chunk()`."
                     % (enc_chunks_tuple, dchunks, var_chunks))
         return enc_chunks_tuple