Declare tornado and traitlets as dependencies explicitly

.github/workflows/test.yaml

@@ -86,6 +86,17 @@ jobs:
             python-version: "3.8"
             pip-extras: lab
 
+          # this test is manually updated to reflect the lower bounds of
+          # versions from dependencies
+          - os: ubuntu-22.04
+            python-version: "3.8"
+            pip-extras: classic
+            pip-install-constraints: >-
+              jupyter-server==1.0
+              simpervisor==1.0
+              tornado==5.0
+              traitlets==4.2.1
+
     steps:
       - uses: actions/checkout@v4
 
@@ -108,7 +119,7 @@ jobs:
         #
         #       Pytest options are set in `pyproject.toml`.
         run: |
-          pip install -vv $(ls ./dist/*.whl)\[acceptance,${{ matrix.pip-extras }}\]
+          pip install -vv $(ls ./dist/*.whl)\[acceptance,${{ matrix.pip-extras }}\] ${{ matrix.pip-install-constraints }}
 
       - name: List Python packages
         run: |

pyproject.toml

@@ -50,6 +50,8 @@ dependencies = [
     "importlib_metadata >=4.8.3 ; python_version<\"3.10\"",
     "jupyter-server >=1.0",
     "simpervisor >=1.0",
+    "tornado >=5.0",
+    "traitlets >= 4.2.1",
 ]
 
 [project.optional-dependencies]