test: show more info when running nightlies

Author: nedbat

.github/workflows/python-nightly.yml

@@ -59,11 +59,16 @@ jobs:
         with:
           python-version: "${{ matrix.python-version }}"
 
-      - name: "Install dependencies"
+      - name: "Show diagnostic info"
         run: |
           set -xe
           python -VV
           python -m site
+          python -m coverage debug sys
+          python -m coverage debug pybehave
+
+      - name: "Install dependencies"
+        run: |
           python -m pip install -r requirements/tox.pip
 
       - name: "Run tox"