python3: update tox to check against both python versions

Jenkinsfile

@@ -16,7 +16,7 @@ pipeline {
                         utils.publish_coverage_native('index.html')
                         utils.publish_pylint('pylint.out')
                     }
-                    junit '*_results.xml'
+                    mergeJunitResults()
                 }
             }
         }

tox.ini

@@ -1,6 +1,6 @@
 [tox]
-envlist = py27-django111
-toxworkdir = {env:TMPDIR:/tmp}/tox-{env:USER}/welco/
+envlist = py27-django111-coverage-pylint,py3-django111
+toxworkdir = {env:TMPDIR:/tmp}/tox-{env:USER}/welco/{env:BRANCH_NAME:}
 
 [testenv]
 usedevelop =
@@ -9,12 +9,13 @@ setenv =
   DJANGO_SETTINGS_MODULE=welco.settings
   WELCO_SETTINGS_FILE=tests/settings.py
   fast: FAST=--nomigrations
+  coverage: COVERAGE=--junitxml=junit-{envname}.xml --cov-report xml --cov-report html --cov=welco/
 deps =
   django111: django>=1.11,<1.12
   pytest-cov
   pytest-django
-  pytest<4.1
-  attrs<19.2
+  pytest!=5.3.3
+  attrs
   WebTest
   mock
   httmock
@@ -26,5 +27,5 @@ deps =
   lxml
   git+https://git.entrouvert.org/debian/django-ckeditor.git
 commands =
-  django111: ./pylint.sh welco/
-  django111: py.test {posargs: --junitxml=test_{envname}_results.xml --cov-report xml --cov-report html --cov=welco/ tests/}
+  pylint: ./pylint.sh welco/
+  py.test {env:COVERAGE:} {posargs:tests/}