build: Fix installation issues in modern Python 3.8+

.github/workflows/ci-build.yml

@@ -138,6 +138,10 @@ jobs:
       - name: Create search_api_mapping.json
         run: cp datagateway_api/search_api_mapping.json.example datagateway_api/search_api_mapping.json
 
+       # See comment in noxfile.py for explanation regarding this step
+      - name: Downgrade setuptools
+        run: poetry run pip install --upgrade setuptools==70.0.0
+        if: matrix.python-version == '3.8' || matrix.python-version == '3.9' || matrix.python-version == '3.10'
       - name: Install dependencies
         run: poetry install
 
@@ -284,6 +288,9 @@ jobs:
       - name: Install Requests
         run: pip install 'requests<2.30'
 
+      # See comment in noxfile.py for explanation regarding this step
+      - name: Downgrade setuptools
+        run: poetry run pip install --upgrade setuptools==70.0.0
       - name: Install dependencies
         run: poetry install
 
@@ -339,6 +346,9 @@ jobs:
       - name: Create search_api_mapping.json
         run: cd /home/runner/work/datagateway-api/datagateway-api; cp datagateway_api/search_api_mapping.json.example datagateway_api/search_api_mapping.json
 
+      # See comment in noxfile.py for explanation regarding this step
+      - name: Downgrade setuptools
+        run: poetry run pip install --upgrade setuptools==70.0.0
       - name: Install dependencies
         run: poetry install
 

noxfile.py

@@ -198,12 +198,23 @@ def safety(session):
 @nox.session(python=["3.6", "3.7", "3.8", "3.9", "3.10"], reuse_venv=True)
 def unit_tests(session):
     args = session.posargs
+    # Explicitly installing/downgrading setuptools is done to fix poetry install on 3.8+
+    # as per https://github.com/pypa/setuptools/issues/4483#issuecomment-2236327987.
+    # A cleaner fix would be to upgrade the packaging library to 22.0+ (as per
+    # https://github.com/pypa/setuptools/issues/4483#issuecomment-2236339726) but this
+    # cannot be done on this repo until support for Python 3.6 is dropped
+    if session.python in ["3.8", "3.9", "3.10"]:
+        session.run("pip", "install", "--upgrade", "setuptools==70.0.0")
     session.run("poetry", "install", external=True)
     session.run("pytest", "test/unit", *args)
 
 
 @nox.session(python=["3.6", "3.7", "3.8", "3.9", "3.10"], reuse_venv=True)
 def integration_tests(session):
     args = session.posargs
+    # Explicit downgrade of setuptools also performed here. See explanation in
+    # `unit_tests()`
+    if session.python in ["3.8", "3.9", "3.10"]:
+        session.run("pip", "install", "--upgrade", "setuptools==70.0.0")
     session.run("poetry", "install", external=True)
     session.run("pytest", "test/integration", *args)