Add official support for Django 2.2. Improve coverage

.travis.yml

@@ -1,54 +1,24 @@
-dist: trusty
+dist: bionic
 sudo: false
 language: python
-env:
-  matrix:
-  - TOXENV=flake8
-  - TOXENV=isort
 cache: pip
-matrix:
+python:
+  - 2.7
+  - 3.5
+  - 3.6
+  - 3.7
+  - 3.8
+stages:
+  - lint
+  - test
+jobs:
   fast_finish: true
   include:
-  - python: 2.7
-    env: TOXENV=py27-1.11
-  - python: 3.4
-    env: TOXENV=py34-1.11
-  - python: 3.4
-    env: TOXENV=py34-2.0
-  - python: 3.5
-    env: TOXENV=py35-1.11
-  - python: 3.5
-    env: TOXENV=py35-2.0
-  - python: 3.5
-    env: TOXENV=py35-2.1
-  - python: 3.5
-    env: TOXENV=py35-master
-  - python: 3.6
-    env: TOXENV=py36-1.11
-  - python: 3.6
-    env: TOXENV=py36-2.0
-  - python: 3.6
-    env: TOXENV=py36-2.1
-  - python: 3.6
-    env: TOXENV=py36-master
-  - python: 3.7
-    env: TOXENV=py37-2.0
-    dist: xenial
-    sudo: true
-  - python: 3.7
-    env: TOXENV=py37-2.1
-    dist: xenial
-    sudo: true
-  - python: 3.7
-    env: TOXENV=py37-master
-    dist: xenial
-    sudo: true
-  allow_failures:
-  - env: TOXENV=py35-master
-  - env: TOXENV=py36-master
-  - env: TOXENV=py37-master
+    - { stage: lint, env: TOXENV=flake8, python: 3.6 }
+    - { stage: lint, env: TOXENV=isort, python: 3.6 }
+
 install:
-- pip install tox coveralls
+- pip install tox coveralls tox-travis
 script:
 - tox
 after_success:

picklefield/fields.py

@@ -4,7 +4,6 @@
 from copy import deepcopy
 from zlib import compress, decompress
 
-import django
 from django.core import checks
 from django.db import models
 from django.utils.encoding import force_text
@@ -170,12 +169,8 @@ def pre_save(self, model_instance, add):
         value = super(PickledObjectField, self).pre_save(model_instance, add)
         return wrap_conflictual_object(value)
 
-    if django.VERSION < (2, 0):
-        def from_db_value(self, value, expression, connection, context):
-            return self.to_python(value)
-    else:
-        def from_db_value(self, value, expression, connection):
-            return self.to_python(value)
+    def from_db_value(self, value, expression, connection, context=None):
+        return self.to_python(value)
 
     def get_db_prep_value(self, value, connection=None, prepared=False):
         """

setup.py

@@ -23,6 +23,7 @@
         'Framework :: Django :: 1.11',
         'Framework :: Django :: 2.0',
         'Framework :: Django :: 2.1',
+        'Framework :: Django :: 2.2',
         'Intended Audience :: Developers',
         'License :: OSI Approved :: MIT License',
         'Operating System :: OS Independent',

tests/models.py

@@ -27,6 +27,7 @@ class TestingModel(models.Model):
     default_pickle_field = PickledObjectField(default=(D1, S1, T1, L1))
     callable_pickle_field = PickledObjectField(default=date.today)
     non_copying_field = PickledObjectField(copy=False, default=TestCopyDataType('boom!'))
+    nullable_pickle_field = PickledObjectField(null=True)
 
 
 class MinimalTestingModel(models.Model):

tests/tests.py

@@ -35,6 +35,7 @@ def test_data_integrity(self):
             # the same data, even thought it's stored differently in the DB.
             self.assertEqual(value, model_test.pickle_field)
             self.assertEqual(value, model_test.compressed_pickle_field)
+            self.assertEqual(None, model_test.nullable_pickle_field)
             # Make sure we can also retrieve the model
             model_test.save()
             model_test.delete()

tox.ini

@@ -4,11 +4,15 @@ args_are_paths = false
 envlist =
     flake8,
     isort,
-    py27-1.11,
-    py34-{1.11,2.0},
-    py35-{1.11,2.0,2.1,master},
-    py36-{1.11,2.0,2.1,master},
-    py37-{1.11,2.0,2.1,master}
+    py{27,34,35,36,37,38}-1.11,
+    py{35,36,37,38}-{2.0,2.1,2.2,master}
+
+[tox:travis]
+3.4 = py34
+3.5 = py35
+3.6 = py36
+3.7 = py37
+3.8 = py38
 
 [testenv]
 basepython =
@@ -17,15 +21,17 @@ basepython =
     py35: python3.5
     py36: python3.6
     py37: python3.7
+    py38: python3.8
 usedevelop = true
 commands =
-    {envpython} -R -Wonce {envbindir}/coverage run -m django test -v2 --settings=tests.settings {posargs}
-    coverage report
+    {envpython} -R -Wonce {envbindir}/coverage run --branch -m django test -v2 --settings=tests.settings {posargs}
+    coverage report -m
 deps =
     coverage
     1.11: Django>=1.11,<2.0
     2.0: Django>=2.0,<2.1
     2.1: Django>=2.1,<2.2
+    2.2: Django>=2.2,<3.0
     master: https://github.com/django/django/archive/master.tar.gz
 
 [testenv:flake8]