CI test suites with pinned minimum dependencies (#3346)

* CI test suites with pinned minimum dependencies

* code review

* Clarity re lxml

azure-pipelines.yml

@@ -8,8 +8,12 @@ jobs:
 - job: Linux
   strategy:
     matrix:
-      py35-min:
-        conda_env: py35-min
+      py35-bare-minimum:
+        conda_env: py35-bare-minimum
+      py36-min-all-deps:
+        conda_env: py36-min-all-deps
+      py36-min-nep18:
+        conda_env: py36-min-nep18
       py36:
         conda_env: py36
       py37:

ci/requirements/py36-min-all-deps.yml

@@ -0,0 +1,43 @@
+name: xarray-tests
+channels:
+  - conda-forge
+dependencies:
+  - python=3.6.7
+  - black
+  - boto3=1.9.235
+  - bottleneck=1.2.1
+  - cdms2=3.1.3
+  - cfgrib=0.9.7.2
+  - cftime=1.0.3.4
+  - coveralls
+  - dask=2.4.0
+  - distributed=2.4.0
+  - flake8
+  - h5netcdf=0.7.4
+  - h5py=2.10.0
+  - hdf5=1.10.5
+  - hypothesis
+  - iris=2.2.0
+  - lxml=4.4.1  # optional dep of pydap
+  - matplotlib=3.1.1
+  - mypy==0.720  # Must match .pre-commit-config.yaml
+  - nc-time-axis=1.2.0
+  - netcdf4=1.5.1.2
+  - numba=0.45.1
+  - numpy=1.17.2
+  - pandas=0.25.1
+  - pip
+  - pseudonetcdf=3.0.2
+  - pydap=3.2.2
+  - pynio=1.5.5
+  - pytest
+  - pytest-cov
+  - pytest-env
+  - rasterio=1.0.28
+  - scipy=1.3.1
+  - seaborn=0.9.0
+  # - sparse  # See py36-min-nep18.yml
+  - toolz=0.10.0
+  - zarr=2.3.2
+  - pip:
+    - numbagg==0.1

ci/requirements/py36-min-nep18.yml

@@ -0,0 +1,17 @@
+name: xarray-tests
+channels:
+  - conda-forge
+dependencies:
+  # Optional dependencies that require NEP18, such as sparse,
+  # require drastically newer packages than everything else
+  - python=3.6.7
+  - coveralls
+  - dask=2.4.0
+  - distributed=2.4.0
+  - numpy=1.17
+  - pandas=0.25
+  - pytest
+  - pytest-cov
+  - pytest-env
+  - scipy=1.3
+  - sparse=0.8.0

ci/requirements/py36.yml

@@ -15,9 +15,10 @@ dependencies:
   - flake8
   - h5netcdf
   - h5py
+  - hdf5
   - hypothesis
   - iris>=1.10
-  - lxml
+  - lxml    # optional dep of pydap
   - matplotlib
   - mypy==0.720  # Must match .pre-commit-config.yaml
   - nc-time-axis

ci/requirements/py37-windows.yml

@@ -15,9 +15,10 @@ dependencies:
   - flake8
   - h5netcdf
   - h5py
+  - hdf5
   - hypothesis
   - iris>=1.10
-  - lxml
+  - lxml    # optional dep of pydap
   - matplotlib
   - mypy==0.720  # Must match .pre-commit-config.yaml
   - nc-time-axis

ci/requirements/py37.yml

@@ -15,9 +15,10 @@ dependencies:
   - flake8
   - h5netcdf
   - h5py
+  - hdf5
   - hypothesis
   - iris>=1.10
-  - lxml
+  - lxml    # optional dep of pydap
   - matplotlib
   - mypy==0.720  # Must match .pre-commit-config.yaml
   - nc-time-axis

xarray/tests/test_plot.py

@@ -1962,7 +1962,7 @@ def test_datetime_hue(self, hue_style):
         ds2.plot.scatter(x="A", y="B", hue="hue", hue_style=hue_style)
 
     def test_facetgrid_hue_style(self):
-        # Can't move this to pytest.mark.parametrize because py35-min
+        # Can't move this to pytest.mark.parametrize because py35-bare-minimum
         # doesn't have mpl.
         for hue_style, map_type in zip(
             ["discrete", "continuous"], [list, mpl.collections.PathCollection]