Pin xarray to get ci passing (#42715)

Author: phofl

environment.yml

@@ -108,7 +108,7 @@ dependencies:
   - fsspec>=0.7.4, <2021.6.0  # for generic remote file operations
   - gcsfs>=0.6.0  # file IO when using 'gcs://...' path
   - sqlalchemy  # pandas.read_sql, DataFrame.to_sql
-  - xarray  # DataFrame.to_xarray
+  - xarray<0.19  # DataFrame.to_xarray
   - cftime  # Needed for downstream xarray.CFTimeIndex test
   - pyreadstat  # pandas.read_spss
   - tabulate>=0.8.3  # DataFrame.to_markdown

requirements-dev.txt

@@ -72,7 +72,7 @@ s3fs>=0.4.0
 fsspec>=0.7.4, <2021.6.0
 gcsfs>=0.6.0
 sqlalchemy
-xarray
+xarray<0.19
 cftime
 pyreadstat
 tabulate>=0.8.3