Try to fix olddeps

.ci/scripts/test_old_deps.sh

@@ -17,4 +17,16 @@ export LANG="C.UTF-8"
 # Prevent virtualenv from auto-updating pip to an incompatible version
 export VIRTUALENV_NO_DOWNLOAD=1
 
-exec tox -e py3-old
+# I'd prefer to use something like this
+#   https://github.com/python-poetry/poetry/issues/3527
+#   https://github.com/pypa/pip/issues/8085
+# rather than this sed script. But that's an Opinion.
+
+# patch the project definitions in-place
+# replace all lower bounds with exact bounds
+# delete all lines referring to psycopg2 --- so no postgres support
+
+# but make the pyopenssl 17.0, which can work against an
+  #    # OpenSSL 1.1 compiled cryptography (as older ones don't compile on Travis).
+sed -i -e "s/[~>]=/==/g" -e "/psycopg2/d" pyproject.toml
+pip install -e .[all]

.github/workflows/tests.yml

@@ -126,8 +126,7 @@ jobs:
         with:
           workdir: /github/workspace
           entrypoint: .ci/scripts/test_old_deps.sh
-        env:
-          TRIAL_FLAGS: "--jobs=2"
+      - run: trial --jobs=2 tests
       - name: Dump logs
         # Logs are most useful when the command fails, always include them.
         if: ${{ always() }}