Use Mamba for refreshing lock-files (#4966)

* Temporarily enable lockfile refresh on push - for testing.

* Temporarily enable lockfile refresh on push - for testing.

* Temporarily enable lockfile refresh on push - for testing.

* Use mamba for lock-file generation.

* Simpler package installation.

* Add Mamba warning to update_lockfiles.py.

* Undo temporary testing changes.

.github/workflows/ci-wheels.yml

@@ -163,4 +163,4 @@ jobs:
       with:
         user: __token__
         password: ${{ secrets.PYPI_API_TOKEN }}
-        print_hash: true
+        print_hash: true

.github/workflows/refresh-lockfiles.yml

@@ -48,11 +48,13 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
-      - name: install conda-lock
+      - name: install requirements
         run: |
           source $CONDA/bin/activate base
-          conda install -y -c conda-forge conda-lock
+          conda install -y -c conda-forge conda-libmamba-solver conda-lock
       - name: generate lockfile
+        env:
+          CONDA_EXPERIMENTAL_SOLVER: libmamba
         run: |
           $CONDA/bin/conda-lock lock -k explicit -p linux-64 -f requirements/ci/${{matrix.python}}.yml
           mv conda-linux-64.lock ${{matrix.python}}-linux-64.lock

tools/update_lockfiles.py

@@ -17,6 +17,15 @@
 from pathlib import Path
 import subprocess
 import sys
+from warnings import warn
+
+
+message = (
+    "Iris' large requirements may require Mamba to successfully solve. If you "
+    "don't want to install Mamba, consider using the workflow_dispatch on "
+    "Iris' GitHub action."
+)
+warn(message)
 
 
 try:
@@ -29,9 +38,9 @@
     "Iris Lockfile Generator",
 )
 
-parser.add_argument('files', nargs='+', 
+parser.add_argument('files', nargs='+',
     help="List of environment.yml files to lock")
-parser.add_argument('--output-dir', '-o', default='.', 
+parser.add_argument('--output-dir', '-o', default='.',
     help="Directory to save output lock files")
 
 args = parser.parse_args()
@@ -43,7 +52,7 @@
     ftype = fname.split('.')[-1]
     if ftype.lower() in ('yaml', 'yml'):
         fname = '.'.join(fname.split('.')[:-1])
-    
+
     # conda-lock --filename-template expects a string with a "...{platform}..."
     # placeholder in it, so we have to build the .lock filname without
     # using .format