moving the mixins to their own module to hide them in stackframes

Reference:
https://mail.python.org/pipermail/python-list/2012-October/632386.html

tests/__init__.py

@@ -1,38 +1,6 @@
 import os
 import sys
-import warnings
 
 sys.path.insert(0, os.path.join(os.path.dirname(os.path.abspath(__file__)),
                                 '../src'))
 
-class _AssertWarnsContext(object):
-    def __init__(self, warningtype, testcase, msg=''):
-        self.warningtype = warningtype
-        warnings.filterwarnings('error')
-        self.failureException = testcase.failureException
-
-    def __enter__(self):
-        return self
-
-    def __exit__(self, exc_type, exc_value, tb):
-        if exc_type is None:
-            try:
-                exc_name = self.warningtype.__name__
-            except AttributeError:
-                exc_name = str(self.warningtype)
-            raise self.failureException(
-                "{0} not raised".format(exc_name))
-
-        if not issubclass(exc_type, self.warningtype):
-            raise self.failureException('"%s" does not match "%s"' %
-                    (self.warningtype.__name__, str(exc_type.__name__)))
-
-        return True
-
-class CatchWarningsMixin(object):
-    def assertWarns(self, wrnClass, callableObj=None, *args, **kwargs):
-        context = _AssertWarnsContext(wrnClass, self)
-        if callableObj is None:
-            return context
-        with context:
-            callableObj(*args, **kwargs)

tests/mixins.py

@@ -0,0 +1,35 @@
+import warnings
+
+__unittest=True
+
+class _AssertWarnsContext(object):
+    def __init__(self, warningtype, testcase, msg=''):
+        self.warningtype = warningtype
+        warnings.filterwarnings('error')
+        self.failureException = testcase.failureException
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_value, tb):
+        if exc_type is None:
+            try:
+                exc_name = self.warningtype.__name__
+            except AttributeError:
+                exc_name = str(self.warningtype)
+            raise self.failureException(
+                "{0} not raised".format(exc_name))
+
+        if not issubclass(exc_type, self.warningtype):
+            raise self.failureException('"%s" does not match "%s"' %
+                    (self.warningtype.__name__, str(exc_type.__name__)))
+
+        return True
+
+class CatchWarningsMixin(object):
+    def assertWarns(self, wrnClass, callableObj=None, *args, **kwargs):
+        context = _AssertWarnsContext(wrnClass, self)
+        if callableObj is None:
+            return context
+        with context:
+            callableObj(*args, **kwargs)

tests/test_distgit.py

@@ -1,7 +1,6 @@
 import unittest
 
-
-from . import CatchWarningsMixin
+from mixins import CatchWarningsMixin
 from centpkg import DistGitDirectory
 
 class TestDistGitNothing(unittest.TestCase):