Show DeprecationWarning, etc. in runtests

Install default warnings filter in test runs, to avoid
python's default suppression of DeprecationWarning
and other "intended for developer" warnings.

(Avoids need to provide -Wd or -Wall arg to runtests.)

.travis.yml

@@ -35,4 +35,4 @@ install:
   - pip install $DJANGO
   - pip install .
   - pip list
-script: python -Wall setup.py test
+script: python setup.py test

docs/contributing.rst

@@ -66,17 +66,18 @@ To run the tests, either:
 
     .. code-block:: console
 
-        $ python -Wall setup.py test
+        $ python setup.py test
 
 or:
 
     .. code-block:: console
 
-        $ python -Wall runtests.py
+        $ python runtests.py
 
 Anymail also includes some integration tests, which do call the live ESP APIs.
 These integration tests require API keys (and sometimes other settings) they
-get from from environment variables. Look in the ``*_integration_tests.py``
+get from from environment variables. They're skipped if these keys aren't present.
+If you want to run them, look in the ``*_integration_tests.py``
 files in the `tests source`_ for specific requirements.
 
 .. _.travis.yml: https://github.com/anymail/django-anymail/blob/master/.travis.yml

runtests.py

@@ -3,11 +3,13 @@
 # python runtests.py [anymail.tests.test_x anymail.tests.test_y.SomeTestCase ...]
 
 import sys
+import warnings
 
 from django import setup
 from django.conf import settings
 from django.test.runner import DiscoverRunner as TestRunner
 
+warnings.simplefilter('default')  # show DeprecationWarning and other default-ignored warnings
 
 APP = 'anymail'