install nightly xarray as a separate step

Author: keewis

.github/workflows/ci.yaml

@@ -65,6 +65,10 @@ jobs:
             python=${{matrix.python-version}}
             conda
 
+      - name: Install nightly xarray
+        run: |
+          python -m pip install --upgrade --pre -i https://pypi.anaconda.org/scientific-python-nightly-wheels/simple xarray
+
       - name: Install xarray-array-testing
         run: |
           python -m pip install --no-deps -e .

ci/requirements/environment.yaml

@@ -10,7 +10,3 @@ dependencies:
   - hypothesis
   - xarray
   - numpy
-  - pip
-  - pip:
-      - --upgrade --pre -i https://pypi.anaconda.org/scientific-python-nightly-wheels/simple --extra-index-url https://pypi.org/simple
-      - xarray