Simplify GH Actions tests workflow

.github/workflows/python-tests.yml

-name: Test suite
+name: >-
+  👷
+  Test suite
 
 on:
   push:
@@ -8,7 +10,10 @@ on:
 
 jobs:
   tests:
-    name: 👷
+    name: >-
+      ${{ matrix.python-version }}
+      /
+      ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
     strategy:
       # max-parallel: 5
@@ -25,11 +30,10 @@ jobs:
         - macOS-latest
         # - windows-2019
         # - windows-2016
-        env:
-        - TOXENV: python
 
     env:
       TOX_PARALLEL_NO_SPINNER: 1
+      TOXENV: python
 
     steps:
     - uses: actions/checkout@master
@@ -43,7 +47,10 @@ jobs:
     - name: Log Python location
       run: >-
         which python
-    - name: Cache pip
+    - name: Log Python env
+      run: >-
+        python -m sysconfig
+    - name: Pip cache
       uses: actions/cache@v1
       with:
         path: ~/.cache/pip
@@ -64,10 +71,13 @@ jobs:
     - name: Log installed dists
       run: >-
         python -m pip freeze --all
+    - name: Adjust TOXENV for PyPy
+      if: startsWith(matrix.python-version, 'pypy')
+      run: >-
+        echo "::set-env name=TOXENV::${{ matrix.python-version }}"
     - name: Log env vars
       run: >-
         env
-      env: ${{ matrix.env }}
 
     - name: Verify that there's no cached Python modules in sources
       if: >-
@@ -76,20 +86,16 @@ jobs:
         ! grep pyc setuptools.egg-info/SOURCES.txt
 
     - name: 'Initialize tox envs: ${{ matrix.env.TOXENV }}'
-      run: |
-        ${{ startsWith(matrix.os, 'windows-') && 'setx TOXENV ' || 'export TOXENV=' }}${{ ('2.7' == matrix.python-version && 'py27') || ('pypy2' == matrix.python-version && 'pypy2') || '$TOXENV' }}
-        ${{ startsWith(matrix.os, 'macOS-') && 'pypy3' == matrix.python-version  && 'export TOXENV=pypy3' || '' }}
-        echo TOXENV="$TOXENV"
-        python -m tox --parallel auto --notest --skip-missing-interpreters false
-      env: ${{ matrix.env }}
+      run: >-
+        python -m
+        tox
+        --parallel auto
+        --notest
+        --skip-missing-interpreters false
     - name: Test with tox
-      run: |
-        ${{ startsWith(matrix.os, 'windows-') && 'setx NETWORK_REQUIRED ' || 'export NETWORK_REQUIRED=' }}1
-        ${{ startsWith(matrix.os, 'windows-') && 'setx TOXENV ' || 'export TOXENV=' }}${{ ('2.7' == matrix.python-version && 'py27') || ('pypy2' == matrix.python-version && 'pypy2') || '$TOXENV' }}
-        ${{ startsWith(matrix.os, 'macOS-') && 'pypy3' == matrix.python-version  && 'export TOXENV=pypy3' || '' }}
-        echo TOXENV="$TOXENV"
-        python -m tox \
-        --parallel 0 \
-        -- \
+      run: >-
+        python -m
+        tox
+        --parallel auto
+        --
         --cov
-      env: ${{ matrix.env }}