Pin iris<3.0.4 to ensure we still (sort of) support Python 3.6

environment.yml

@@ -9,7 +9,7 @@ dependencies:
   - compilers
   - fiona  # 1.8.18/py39, they seem weary to build manylinux wheels and pypi ver built with older gdal
   - esmpy
-  - iris>=3.0.2  # bump to latest to have a number of bugfixes available
+  - iris>=3.0.2,<3.0.4  # iris=3.0.4 dropped support for Python 3.6 but we haven't just yet (23 July 2021, bugfix release 2.3.1)
   - graphviz
   - python>=3.6
   - python-stratify

package/meta.yaml

@@ -37,7 +37,7 @@ requirements:
     # esmvaltool
     - python>=3.6
     - graphviz
-    - iris>=3.0.2
+    - iris>=3.0.2,<3.0.4  # iris=3.0.4 dropped support for Python 3.6 but we haven't just yet (23 July 2021, bugfix release 2.3.1)
     - python-stratify
     - scipy<1.6  # until ESMValGroup/ESMValCore/issues/927 gets resolved
     # Normally installed via pip:

setup.py

@@ -44,7 +44,7 @@
         'pybtex',
         'pyyaml',
         'requests',
-        'scitools-iris>=3.0.2',
+        'scitools-iris>=3.0.2,<3.0.4',  # see environment.yml
         'shapely[vectorized]',
         'stratify',
         'yamale',