Test both with and without smtp extra

Author: mgorny

.github/workflows/tests.yml

@@ -12,6 +12,7 @@ jobs:
         # Not all Python versions are available for linux AND x64
         # https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json
         python-version: [3.5, 3.6, 3.7, 3.8, 3.9, '3.10']
+        extra: ['', '-smtp']
       fail-fast: false
 
     steps:
@@ -25,4 +26,4 @@ jobs:
         python -m pip install --upgrade pip
         pip install tox
     - name: Test with tox
-      run: tox -vv -e py
+      run: tox -vv -e py${{ matrix.extra }}

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py35,py36,py37,py38,py39,py310
+envlist = py{35,36,37,38,39,310}{,-smtp}
 recreate = True
 isolated_build = True
 
@@ -16,7 +16,7 @@ deps =
     six
     requests
 extras =
-    smtp
+    smtp: smtp
 commands =
   pytest -v \
     --junitxml=junit-{envname}.xml \