django22: declare django2.2 in tox (#51168)

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 toxworkdir = {env:TMPDIR:/tmp}/tox-{env:USER}/passerelle-reunion-unicite/{env:BRANCH_NAME:}
-envlist = py3-django111
+envlist = py3-{django111,django22}
 
 [testenv]
 usedevelop = True
@@ -9,10 +9,11 @@ setenv =
   PASSERELLE_SETTINGS_FILE=tests/settings.py
 deps =
   django111: django>=1.11,<1.12
+  django22: django>=2.2,<2.3
   git+https://git.entrouvert.org/passerelle.git
   django-webtest
   psycopg2-binary
   pytest
   pytest-django
 commands =
-  django111: py.test {posargs: --junitxml=junit-{envname}.xml tests/}
+  py.test {posargs: --junitxml=junit-{envname}.xml tests/}